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{"kind": "coding_drills", "role_id": "role_G5ptCSSXUc4", "source": "leetcode_graphql", "generated_at": "2026-07-17T22:12:40.332029+00:00", "difficulty_mix": {"Easy": 3, "Medium": 5, "Hard": 2}, "topics_filter": [], "questions": [{"index": 0, "category": "coding_array", "question": "[Easy] LC #1 \u00b7 Two Sum \u2014 solve on leetcode.com", "why": "Topic tags: array, hash-table. AC rate 57.5%. Open the editor at https://leetcode.com/problems/two-sum/, talk through your approach, then sketch the algorithm here (whiteboard) or write a plain-English solution (typed).", "how_to_prepare": "Clarify constraints, propose a brute-force, refine to an optimal time/space, walk through 2 example inputs (including an edge case), then trace your final code by hand.", "leetcode": {"title_slug": "two-sum", "frontend_id": "1", "difficulty": "Easy", "ac_rate": 57.49451107379435, "topics": ["array", "hash-table"], "url": "https://leetcode.com/problems/two-sum/", "problem_html": "<p>Given an array of integers <code>nums</code> and an integer <code>target</code>, return <em>indices of the two numbers such that they add up to <code>target</code></em>.</p>\n\n<p>You may assume that each input would have <strong><em>exactly</em> one solution</strong>, and you may not use the <em>same</em> element twice.</p>\n\n<p>You can return the answer in any order.</p>\n\n<p> </p>\n<p><strong class=\"example\">Example 1:</strong></p>\n\n<pre>\n<strong>Input:</strong> nums = [2,7,11,15], target = 9\n<strong>Output:</strong> [0,1]\n<strong>Explanation:</strong> Because nums[0] + nums[1] == 9, we return [0, 1].\n</pre>\n\n<p><strong class=\"example\">Example 2:</strong></p>\n\n<pre>\n<strong>Input:</strong> nums = [3,2,4], target = 6\n<strong>Output:</strong> [1,2]\n</pre>\n\n<p><strong class=\"example\">Example 3:</strong></p>\n\n<pre>\n<strong>Input:</strong> nums = [3,3], target = 6\n<strong>Output:</strong> [0,1]\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>2 <= nums.length <= 10<sup>4</sup></code></li>\n\t<li><code>-10<sup>9</sup> <= nums[i] <= 10<sup>9</sup></code></li>\n\t<li><code>-10<sup>9</sup> <= target <= 10<sup>9</sup></code></li>\n\t<li><strong>Only one valid answer exists.</strong></li>\n</ul>\n\n<p> </p>\n<strong>Follow-up: </strong>Can you come up with an algorithm that is less than <code>O(n<sup>2</sup>)</code><font face=\"monospace\"> </font>time complexity?", "hints": ["A really brute force way would be to search for all possible pairs of numbers but that would be too slow. Again, it's best to try out brute force solutions just for completeness. It is from these brute force solutions that you can come up with optimizations.", "So, if we fix one of the numbers, say <code>x</code>, we have to scan the entire array to find the next number <code>y</code> which is <code>value - x</code> where value is the input parameter. Can we change our array somehow so that this search becomes faster?", "The second train of thought is, without changing the array, can we use additional space somehow? Like maybe a hash map to speed up the search?"]}}, {"index": 1, "category": "coding_array", "question": "[Easy] LC #14 \u00b7 Longest Common Prefix \u2014 solve on leetcode.com", "why": "Topic tags: array, string, trie. AC rate 47.6%. Open the editor at https://leetcode.com/problems/longest-common-prefix/, talk through your approach, then sketch the algorithm here (whiteboard) or write a plain-English solution (typed).", "how_to_prepare": "Clarify constraints, propose a brute-force, refine to an optimal time/space, walk through 2 example inputs (including an edge case), then trace your final code by hand.", "leetcode": {"title_slug": "longest-common-prefix", "frontend_id": "14", "difficulty": "Easy", "ac_rate": 47.5629941623571, "topics": ["array", "string", "trie"], "url": "https://leetcode.com/problems/longest-common-prefix/", "problem_html": "<p>Write a function to find the longest common prefix string amongst an array of strings.</p>\n\n<p>If there is no common prefix, return an empty string <code>""</code>.</p>\n\n<p> </p>\n<p><strong class=\"example\">Example 1:</strong></p>\n\n<pre>\n<strong>Input:</strong> strs = ["flower","flow","flight"]\n<strong>Output:</strong> "fl"\n</pre>\n\n<p><strong class=\"example\">Example 2:</strong></p>\n\n<pre>\n<strong>Input:</strong> strs = ["dog","racecar","car"]\n<strong>Output:</strong> ""\n<strong>Explanation:</strong> There is no common prefix among the input strings.\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>1 <= strs.length <= 200</code></li>\n\t<li><code>0 <= strs[i].length <= 200</code></li>\n\t<li><code>strs[i]</code> consists of only lowercase English letters if it is non-empty.</li>\n</ul>\n", "hints": []}}, {"index": 2, "category": "coding_string", "question": "[Easy] LC #20 \u00b7 Valid Parentheses \u2014 solve on leetcode.com", "why": "Topic tags: string, stack. AC rate 44.2%. Open the editor at https://leetcode.com/problems/valid-parentheses/, talk through your approach, then sketch the algorithm here (whiteboard) or write a plain-English solution (typed).", "how_to_prepare": "Clarify constraints, propose a brute-force, refine to an optimal time/space, walk through 2 example inputs (including an edge case), then trace your final code by hand.", "leetcode": {"title_slug": "valid-parentheses", "frontend_id": "20", "difficulty": "Easy", "ac_rate": 44.1741531650066, "topics": ["string", "stack"], "url": "https://leetcode.com/problems/valid-parentheses/", "problem_html": "<p>Given a string <code>s</code> containing just the characters <code>'('</code>, <code>')'</code>, <code>'{'</code>, <code>'}'</code>, <code>'['</code> and <code>']'</code>, determine if the input string is valid.</p>\n\n<p>An input string is valid if:</p>\n\n<ol>\n\t<li>Open brackets must be closed by the same type of brackets.</li>\n\t<li>Open brackets must be closed in the correct order.</li>\n\t<li>Every close bracket has a corresponding open bracket of the same type.</li>\n</ol>\n\n<p> </p>\n<p><strong class=\"example\">Example 1:</strong></p>\n\n<div class=\"example-block\">\n<p><strong>Input:</strong> <span class=\"example-io\">s = "()"</span></p>\n\n<p><strong>Output:</strong> <span class=\"example-io\">true</span></p>\n</div>\n\n<p><strong class=\"example\">Example 2:</strong></p>\n\n<div class=\"example-block\">\n<p><strong>Input:</strong> <span class=\"example-io\">s = "()[]{}"</span></p>\n\n<p><strong>Output:</strong> <span class=\"example-io\">true</span></p>\n</div>\n\n<p><strong class=\"example\">Example 3:</strong></p>\n\n<div class=\"example-block\">\n<p><strong>Input:</strong> <span class=\"example-io\">s = "(]"</span></p>\n\n<p><strong>Output:</strong> <span class=\"example-io\">false</span></p>\n</div>\n\n<p><strong class=\"example\">Example 4:</strong></p>\n\n<div class=\"example-block\">\n<p><strong>Input:</strong> <span class=\"example-io\">s = "([])"</span></p>\n\n<p><strong>Output:</strong> <span class=\"example-io\">true</span></p>\n</div>\n\n<p><strong class=\"example\">Example 5:</strong></p>\n\n<div class=\"example-block\">\n<p><strong>Input:</strong> <span class=\"example-io\">s = "([)]"</span></p>\n\n<p><strong>Output:</strong> <span class=\"example-io\">false</span></p>\n</div>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>1 <= s.length <= 10<sup>4</sup></code></li>\n\t<li><code>s</code> consists of parentheses only <code>'()[]{}'</code>.</li>\n</ul>\n", "hints": ["Use a stack of characters.", "When you encounter an opening bracket, push it to the top of the stack.", "When you encounter a closing bracket, check if the top of the stack was the opening for it. If yes, pop it from the stack. Otherwise, return false."]}}, {"index": 3, "category": "coding_hash_table", "question": "[Medium] LC #12 \u00b7 Integer to Roman \u2014 solve on leetcode.com", "why": "Topic tags: hash-table, math, string. AC rate 71.0%. Open the editor at https://leetcode.com/problems/integer-to-roman/, talk through your approach, then sketch the algorithm here (whiteboard) or write a plain-English solution (typed).", "how_to_prepare": "Clarify constraints, propose a brute-force, refine to an optimal time/space, walk through 2 example inputs (including an edge case), then trace your final code by hand.", "leetcode": {"title_slug": "integer-to-roman", "frontend_id": "12", "difficulty": "Medium", "ac_rate": 70.96725114430731, "topics": ["hash-table", "math", "string"], "url": "https://leetcode.com/problems/integer-to-roman/", "problem_html": "<p>Seven different symbols represent Roman numerals with the following values:</p>\n\n<table>\n\t<thead>\n\t\t<tr>\n\t\t\t<th>Symbol</th>\n\t\t\t<th>Value</th>\n\t\t</tr>\n\t</thead>\n\t<tbody>\n\t\t<tr>\n\t\t\t<td>I</td>\n\t\t\t<td>1</td>\n\t\t</tr>\n\t\t<tr>\n\t\t\t<td>V</td>\n\t\t\t<td>5</td>\n\t\t</tr>\n\t\t<tr>\n\t\t\t<td>X</td>\n\t\t\t<td>10</td>\n\t\t</tr>\n\t\t<tr>\n\t\t\t<td>L</td>\n\t\t\t<td>50</td>\n\t\t</tr>\n\t\t<tr>\n\t\t\t<td>C</td>\n\t\t\t<td>100</td>\n\t\t</tr>\n\t\t<tr>\n\t\t\t<td>D</td>\n\t\t\t<td>500</td>\n\t\t</tr>\n\t\t<tr>\n\t\t\t<td>M</td>\n\t\t\t<td>1000</td>\n\t\t</tr>\n\t</tbody>\n</table>\n\n<p>Roman numerals are formed by appending the conversions of decimal place values from highest to lowest. Converting a decimal place value into a Roman numeral has the following rules:</p>\n\n<ul>\n\t<li>If the value does not start with 4 or 9, select the symbol of the maximal value that can be subtracted from the input, append that symbol to the result, subtract its value, and convert the remainder to a Roman numeral.</li>\n\t<li>If the value starts with 4 or 9 use the <strong>subtractive form</strong> representing one symbol subtracted from the following symbol, for example, 4 is 1 (<code>I</code>) less than 5 (<code>V</code>): <code>IV</code> and 9 is 1 (<code>I</code>) less than 10 (<code>X</code>): <code>IX</code>. Only the following subtractive forms are used: 4 (<code>IV</code>), 9 (<code>IX</code>), 40 (<code>XL</code>), 90 (<code>XC</code>), 400 (<code>CD</code>) and 900 (<code>CM</code>).</li>\n\t<li>Only powers of 10 (<code>I</code>, <code>X</code>, <code>C</code>, <code>M</code>) can be appended consecutively at most 3 times to represent multiples of 10. You cannot append 5 (<code>V</code>), 50 (<code>L</code>), or 500 (<code>D</code>) multiple times. If you need to append a symbol 4 times use the <strong>subtractive form</strong>.</li>\n</ul>\n\n<p>Given an integer, convert it to a Roman numeral.</p>\n\n<p> </p>\n<p><strong class=\"example\">Example 1:</strong></p>\n\n<div class=\"example-block\">\n<p><strong>Input:</strong> <span class=\"example-io\">num = 3749</span></p>\n\n<p><strong>Output:</strong> <span class=\"example-io\">"MMMDCCXLIX"</span></p>\n\n<p><strong>Explanation:</strong></p>\n\n<pre>\n3000 = MMM as 1000 (M) + 1000 (M) + 1000 (M)\n 700 = DCC as 500 (D) + 100 (C) + 100 (C)\n 40 = XL as 10 (X) less of 50 (L)\n 9 = IX as 1 (I) less of 10 (X)\nNote: 49 is not 1 (I) less of 50 (L) because the conversion is based on decimal places\n</pre>\n</div>\n\n<p><strong class=\"example\">Example 2:</strong></p>\n\n<div class=\"example-block\">\n<p><strong>Input:</strong> <span class=\"example-io\">num = 58</span></p>\n\n<p><strong>Output:</strong> <span class=\"example-io\">"LVIII"</span></p>\n\n<p><strong>Explanation:</strong></p>\n\n<pre>\n50 = L\n 8 = VIII\n</pre>\n</div>\n\n<p><strong class=\"example\">Example 3:</strong></p>\n\n<div class=\"example-block\">\n<p><strong>Input:</strong> <span class=\"example-io\">num = 1994</span></p>\n\n<p><strong>Output:</strong> <span class=\"example-io\">"MCMXCIV"</span></p>\n\n<p><strong>Explanation:</strong></p>\n\n<pre>\n1000 = M\n 900 = CM\n 90 = XC\n 4 = IV\n</pre>\n</div>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>1 <= num <= 3999</code></li>\n</ul>\n", "hints": []}}, {"index": 4, "category": "coding_array", "question": "[Medium] LC #34 \u00b7 Find First and Last Position of Element in Sorted Array \u2014 solve on leetcode.com", "why": "Topic tags: array, binary-search. AC rate 48.9%. Open the editor at https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/, talk through your approach, then sketch the algorithm here (whiteboard) or write a plain-English solution (typed).", "how_to_prepare": "Clarify constraints, propose a brute-force, refine to an optimal time/space, walk through 2 example inputs (including an edge case), then trace your final code by hand.", "leetcode": {"title_slug": "find-first-and-last-position-of-element-in-sorted-array", "frontend_id": "34", "difficulty": "Medium", "ac_rate": 48.88231611755927, "topics": ["array", "binary-search"], "url": "https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/", "problem_html": "<p>Given an array of integers <code>nums</code> sorted in non-decreasing order, find the starting and ending position of a given <code>target</code> value.</p>\n\n<p>If <code>target</code> is not found in the array, return <code>[-1, -1]</code>.</p>\n\n<p>You must write an algorithm with <code>O(log n)</code> runtime complexity.</p>\n\n<p> </p>\n<p><strong class=\"example\">Example 1:</strong></p>\n<pre><strong>Input:</strong> nums = [5,7,7,8,8,10], target = 8\n<strong>Output:</strong> [3,4]\n</pre><p><strong class=\"example\">Example 2:</strong></p>\n<pre><strong>Input:</strong> nums = [5,7,7,8,8,10], target = 6\n<strong>Output:</strong> [-1,-1]\n</pre><p><strong class=\"example\">Example 3:</strong></p>\n<pre><strong>Input:</strong> nums = [], target = 0\n<strong>Output:</strong> [-1,-1]\n</pre>\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>0 <= nums.length <= 10<sup>5</sup></code></li>\n\t<li><code>-10<sup>9</sup> <= nums[i] <= 10<sup>9</sup></code></li>\n\t<li><code>nums</code> is a non-decreasing array.</li>\n\t<li><code>-10<sup>9</sup> <= target <= 10<sup>9</sup></code></li>\n</ul>\n", "hints": []}}, {"index": 5, "category": "coding_linked_list", "question": "[Medium] LC #2 \u00b7 Add Two Numbers \u2014 solve on leetcode.com", "why": "Topic tags: linked-list, math, recursion. AC rate 48.5%. Open the editor at https://leetcode.com/problems/add-two-numbers/, talk through your approach, then sketch the algorithm here (whiteboard) or write a plain-English solution (typed).", "how_to_prepare": "Clarify constraints, propose a brute-force, refine to an optimal time/space, walk through 2 example inputs (including an edge case), then trace your final code by hand.", "leetcode": {"title_slug": "add-two-numbers", "frontend_id": "2", "difficulty": "Medium", "ac_rate": 48.46758391189911, "topics": ["linked-list", "math", "recursion"], "url": "https://leetcode.com/problems/add-two-numbers/", "problem_html": "<p>You are given two <strong>non-empty</strong> linked lists representing two non-negative integers. The digits are stored in <strong>reverse order</strong>, and each of their nodes contains a single digit. Add the two numbers and return the sum as a linked list.</p>\n\n<p>You may assume the two numbers do not contain any leading zero, except the number 0 itself.</p>\n\n<p> </p>\n<p><strong class=\"example\">Example 1:</strong></p>\n<img alt=\"\" src=\"https://assets.leetcode.com/uploads/2020/10/02/addtwonumber1.jpg\" style=\"width: 483px; height: 342px;\" />\n<pre>\n<strong>Input:</strong> l1 = [2,4,3], l2 = [5,6,4]\n<strong>Output:</strong> [7,0,8]\n<strong>Explanation:</strong> 342 + 465 = 807.\n</pre>\n\n<p><strong class=\"example\">Example 2:</strong></p>\n\n<pre>\n<strong>Input:</strong> l1 = [0], l2 = [0]\n<strong>Output:</strong> [0]\n</pre>\n\n<p><strong class=\"example\">Example 3:</strong></p>\n\n<pre>\n<strong>Input:</strong> l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]\n<strong>Output:</strong> [8,9,9,9,0,0,0,1]\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li>The number of nodes in each linked list is in the range <code>[1, 100]</code>.</li>\n\t<li><code>0 <= Node.val <= 9</code></li>\n\t<li>It is guaranteed that the list represents a number that does not have leading zeros.</li>\n</ul>\n", "hints": []}}, {"index": 6, "category": "coding_string", "question": "[Medium] LC #8 \u00b7 String to Integer (atoi) \u2014 solve on leetcode.com", "why": "Topic tags: string. AC rate 21.0%. Open the editor at https://leetcode.com/problems/string-to-integer-atoi/, talk through your approach, then sketch the algorithm here (whiteboard) or write a plain-English solution (typed).", "how_to_prepare": "Clarify constraints, propose a brute-force, refine to an optimal time/space, walk through 2 example inputs (including an edge case), then trace your final code by hand.", "leetcode": {"title_slug": "string-to-integer-atoi", "frontend_id": "8", "difficulty": "Medium", "ac_rate": 21.000581005954157, "topics": ["string"], "url": "https://leetcode.com/problems/string-to-integer-atoi/", "problem_html": "<p>Implement the <code>myAtoi(string s)</code> function, which converts a string to a 32-bit signed integer.</p>\n\n<p>The algorithm for <code>myAtoi(string s)</code> is as follows:</p>\n\n<ol>\n\t<li><strong>Whitespace</strong>: Ignore any leading whitespace (<code>" "</code>).</li>\n\t<li><strong>Signedness</strong>: Determine the sign by checking if the next character is <code>'-'</code> or <code>'+'</code>, assuming positivity if neither present.</li>\n\t<li><strong>Conversion</strong>: Read the integer by skipping leading zeros until a non-digit character is encountered or the end of the string is reached. If no digits were read, then the result is 0.</li>\n\t<li><strong>Rounding</strong>: If the integer is out of the 32-bit signed integer range <code>[-2<sup>31</sup>, 2<sup>31</sup> - 1]</code>, then round the integer to remain in the range. Specifically, integers less than <code>-2<sup>31</sup></code> should be rounded to <code>-2<sup>31</sup></code>, and integers greater than <code>2<sup>31</sup> - 1</code> should be rounded to <code>2<sup>31</sup> - 1</code>.</li>\n</ol>\n\n<p>Return the integer as the final result.</p>\n\n<p> </p>\n<p><strong class=\"example\">Example 1:</strong></p>\n\n<div class=\"example-block\">\n<p><strong>Input:</strong> <span class=\"example-io\">s = "42"</span></p>\n\n<p><strong>Output:</strong> <span class=\"example-io\">42</span></p>\n\n<p><strong>Explanation:</strong></p>\n\n<pre>\nThe underlined characters are what is read in and the caret is the current reader position.\nStep 1: "42" (no characters read because there is no leading whitespace)\n ^\nStep 2: "42" (no characters read because there is neither a '-' nor '+')\n ^\nStep 3: "<u>42</u>" ("42" is read in)\n ^\n</pre>\n</div>\n\n<p><strong class=\"example\">Example 2:</strong></p>\n\n<div class=\"example-block\">\n<p><strong>Input:</strong> <span class=\"example-io\">s = " -042"</span></p>\n\n<p><strong>Output:</strong> <span class=\"example-io\">-42</span></p>\n\n<p><strong>Explanation:</strong></p>\n\n<pre>\nStep 1: "<u> </u>-042" (leading whitespace is read and ignored)\n ^\nStep 2: " <u>-</u>042" ('-' is read, so the result should be negative)\n ^\nStep 3: " -<u>042</u>" ("042" is read in, leading zeros ignored in the result)\n ^\n</pre>\n</div>\n\n<p><strong class=\"example\">Example 3:</strong></p>\n\n<div class=\"example-block\">\n<p><strong>Input:</strong> <span class=\"example-io\">s = "1337c0d3"</span></p>\n\n<p><strong>Output:</strong> <span class=\"example-io\">1337</span></p>\n\n<p><strong>Explanation:</strong></p>\n\n<pre>\nStep 1: "1337c0d3" (no characters read because there is no leading whitespace)\n ^\nStep 2: "1337c0d3" (no characters read because there is neither a '-' nor '+')\n ^\nStep 3: "<u>1337</u>c0d3" ("1337" is read in; reading stops because the next character is a non-digit)\n ^\n</pre>\n</div>\n\n<p><strong class=\"example\">Example 4:</strong></p>\n\n<div class=\"example-block\">\n<p><strong>Input:</strong> <span class=\"example-io\">s = "0-1"</span></p>\n\n<p><strong>Output:</strong> <span class=\"example-io\">0</span></p>\n\n<p><strong>Explanation:</strong></p>\n\n<pre>\nStep 1: "0-1" (no characters read because there is no leading whitespace)\n ^\nStep 2: "0-1" (no characters read because there is neither a '-' nor '+')\n ^\nStep 3: "<u>0</u>-1" ("0" is read in; reading stops because the next character is a non-digit)\n ^\n</pre>\n</div>\n\n<p><strong class=\"example\">Example 5:</strong></p>\n\n<div class=\"example-block\">\n<p><strong>Input:</strong> <span class=\"example-io\">s = "words and 987"</span></p>\n\n<p><strong>Output:</strong> <span class=\"example-io\">0</span></p>\n\n<p><strong>Explanation:</strong></p>\n\n<p>Reading stops at the first non-digit character 'w'.</p>\n</div>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>0 <= s.length <= 200</code></li>\n\t<li><code>s</code> consists of English letters (lower-case and upper-case), digits (<code>0-9</code>), <code>' '</code>, <code>'+'</code>, <code>'-'</code>, and <code>'.'</code>.</li>\n</ul>\n", "hints": []}}, {"index": 7, "category": "coding_array", "question": "[Medium] LC #33 \u00b7 Search in Rotated Sorted Array \u2014 solve on leetcode.com", "why": "Topic tags: array, binary-search. AC rate 44.5%. Open the editor at https://leetcode.com/problems/search-in-rotated-sorted-array/, talk through your approach, then sketch the algorithm here (whiteboard) or write a plain-English solution (typed).", "how_to_prepare": "Clarify constraints, propose a brute-force, refine to an optimal time/space, walk through 2 example inputs (including an edge case), then trace your final code by hand.", "leetcode": {"title_slug": "search-in-rotated-sorted-array", "frontend_id": "33", "difficulty": "Medium", "ac_rate": 44.5466822595173, "topics": ["array", "binary-search"], "url": "https://leetcode.com/problems/search-in-rotated-sorted-array/", "problem_html": "<p>There is an integer array <code>nums</code> sorted in ascending order (with <strong>distinct</strong> values).</p>\n\n<p>Prior to being passed to your function, <code>nums</code> is <strong>possibly left rotated</strong> at an unknown index <code>k</code> (<code>1 <= k < nums.length</code>) such that the resulting array is <code>[nums[k], nums[k+1], ..., nums[n-1], nums[0], nums[1], ..., nums[k-1]]</code> (<strong>0-indexed</strong>). For example, <code>[0,1,2,4,5,6,7]</code> might be left rotated by <code>3</code> indices and become <code>[4,5,6,7,0,1,2]</code>.</p>\n\n<p>Given the array <code>nums</code> <strong>after</strong> the possible rotation and an integer <code>target</code>, return <em>the index of </em><code>target</code><em> if it is in </em><code>nums</code><em>, or </em><code>-1</code><em> if it is not in </em><code>nums</code>.</p>\n\n<p>You must write an algorithm with <code>O(log n)</code> runtime complexity.</p>\n\n<p> </p>\n<p><strong class=\"example\">Example 1:</strong></p>\n<pre><strong>Input:</strong> nums = [4,5,6,7,0,1,2], target = 0\n<strong>Output:</strong> 4\n</pre><p><strong class=\"example\">Example 2:</strong></p>\n<pre><strong>Input:</strong> nums = [4,5,6,7,0,1,2], target = 3\n<strong>Output:</strong> -1\n</pre><p><strong class=\"example\">Example 3:</strong></p>\n<pre><strong>Input:</strong> nums = [1], target = 0\n<strong>Output:</strong> -1\n</pre>\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>1 <= nums.length <= 5000</code></li>\n\t<li><code>-10<sup>4</sup> <= nums[i] <= 10<sup>4</sup></code></li>\n\t<li>All values of <code>nums</code> are <strong>unique</strong>.</li>\n\t<li><code>nums</code> is an ascending array that is possibly rotated.</li>\n\t<li><code>-10<sup>4</sup> <= target <= 10<sup>4</sup></code></li>\n</ul>\n", "hints": []}}, {"index": 8, "category": "coding_string", "question": "[Hard] LC #44 \u00b7 Wildcard Matching \u2014 solve on leetcode.com", "why": "Topic tags: string, dynamic-programming, greedy, recursion. AC rate 32.0%. Open the editor at https://leetcode.com/problems/wildcard-matching/, talk through your approach, then sketch the algorithm here (whiteboard) or write a plain-English solution (typed).", "how_to_prepare": "Clarify constraints, propose a brute-force, refine to an optimal time/space, walk through 2 example inputs (including an edge case), then trace your final code by hand.", "leetcode": {"title_slug": "wildcard-matching", "frontend_id": "44", "difficulty": "Hard", "ac_rate": 31.971355472696484, "topics": ["string", "dynamic-programming", "greedy", "recursion"], "url": "https://leetcode.com/problems/wildcard-matching/", "problem_html": "<p>Given an input string (<code>s</code>) and a pattern (<code>p</code>), implement wildcard pattern matching with support for <code>'?'</code> and <code>'*'</code> where:</p>\n\n<ul>\n\t<li><code>'?'</code> Matches any single character.</li>\n\t<li><code>'*'</code> Matches any sequence of characters (including the empty sequence).</li>\n</ul>\n\n<p>The matching should cover the <strong>entire</strong> input string (not partial).</p>\n\n<p> </p>\n<p><strong class=\"example\">Example 1:</strong></p>\n\n<pre>\n<strong>Input:</strong> s = "aa", p = "a"\n<strong>Output:</strong> false\n<strong>Explanation:</strong> "a" does not match the entire string "aa".\n</pre>\n\n<p><strong class=\"example\">Example 2:</strong></p>\n\n<pre>\n<strong>Input:</strong> s = "aa", p = "*"\n<strong>Output:</strong> true\n<strong>Explanation:</strong> '*' matches any sequence.\n</pre>\n\n<p><strong class=\"example\">Example 3:</strong></p>\n\n<pre>\n<strong>Input:</strong> s = "cb", p = "?a"\n<strong>Output:</strong> false\n<strong>Explanation:</strong> '?' matches 'c', but the second letter is 'a', which does not match 'b'.\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>0 <= s.length, p.length <= 2000</code></li>\n\t<li><code>s</code> contains only lowercase English letters.</li>\n\t<li><code>p</code> contains only lowercase English letters, <code>'?'</code> or <code>'*'</code>.</li>\n</ul>\n", "hints": []}}, {"index": 9, "category": "coding_string", "question": "[Hard] LC #10 \u00b7 Regular Expression Matching \u2014 solve on leetcode.com", "why": "Topic tags: string, dynamic-programming, recursion. AC rate 31.0%. Open the editor at https://leetcode.com/problems/regular-expression-matching/, talk through your approach, then sketch the algorithm here (whiteboard) or write a plain-English solution (typed).", "how_to_prepare": "Clarify constraints, propose a brute-force, refine to an optimal time/space, walk through 2 example inputs (including an edge case), then trace your final code by hand.", "leetcode": {"title_slug": "regular-expression-matching", "frontend_id": "10", "difficulty": "Hard", "ac_rate": 30.95323848106803, "topics": ["string", "dynamic-programming", "recursion"], "url": "https://leetcode.com/problems/regular-expression-matching/", "problem_html": "<p>Given an input string <code>s</code> and a pattern <code>p</code>, implement regular expression matching with support for <code>'.'</code> and <code>'*'</code> where:</p>\n\n<ul>\n\t<li><code>'.'</code> Matches any single character.\u200b\u200b\u200b\u200b</li>\n\t<li><code>'*'</code> Matches zero or more of the preceding element.</li>\n</ul>\n\n<p>Return a boolean indicating whether the matching covers the entire input string (not partial).</p>\n\n<p> </p>\n<p><strong class=\"example\">Example 1:</strong></p>\n\n<pre>\n<strong>Input:</strong> s = "aa", p = "a"\n<strong>Output:</strong> false\n<strong>Explanation:</strong> "a" does not match the entire string "aa".\n</pre>\n\n<p><strong class=\"example\">Example 2:</strong></p>\n\n<pre>\n<strong>Input:</strong> s = "aa", p = "a*"\n<strong>Output:</strong> true\n<strong>Explanation:</strong> '*' means zero or more of the preceding element, 'a'. Therefore, by repeating 'a' once, it becomes "aa".\n</pre>\n\n<p><strong class=\"example\">Example 3:</strong></p>\n\n<pre>\n<strong>Input:</strong> s = "ab", p = ".*"\n<strong>Output:</strong> true\n<strong>Explanation:</strong> ".*" means "zero or more (*) of any character (.)".\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>1 <= s.length <= 20</code></li>\n\t<li><code>1 <= p.length <= 20</code></li>\n\t<li><code>s</code> contains only lowercase English letters.</li>\n\t<li><code>p</code> contains only lowercase English letters, <code>'.'</code>, and <code>'*'</code>.</li>\n\t<li>It is guaranteed for each appearance of the character <code>'*'</code>, there will be a previous valid character to match.</li>\n</ul>\n", "hints": []}}]}