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| <div><p>The <strong>n-queens</strong> puzzle is the problem of placing <code>n</code> queens on an <code>n x n</code> chessboard such that no two queens attack each other.</p> | ||
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| <p>Given an integer <code>n</code>, return <em>the number of distinct solutions to the <strong>n-queens puzzle</strong></em>.</p> | ||
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| <p> </p> | ||
| <p><strong>Example 1:</strong></p> | ||
| <img alt="" src="https://assets.leetcode.com/uploads/2020/11/13/queens.jpg" style="width: 600px; height: 268px;"> | ||
| <pre><strong>Input:</strong> n = 4 | ||
| <strong>Output:</strong> 2 | ||
| <strong>Explanation:</strong> There are two distinct solutions to the 4-queens puzzle as shown. | ||
| </pre> | ||
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| <p><strong>Example 2:</strong></p> | ||
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| <pre><strong>Input:</strong> n = 1 | ||
| <strong>Output:</strong> 1 | ||
| </pre> | ||
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| <p> </p> | ||
| <p><strong>Constraints:</strong></p> | ||
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| <ul> | ||
| <li><code>1 <= n <= 9</code></li> | ||
| </ul> | ||
| </div> |
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| <div><p>Given an integer array <code>nums</code>, find the contiguous subarray (containing at least one number) which has the largest sum and return <em>its sum</em>.</p> | ||
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| <p> </p> | ||
| <p><strong>Example 1:</strong></p> | ||
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| <pre><strong>Input:</strong> nums = [-2,1,-3,4,-1,2,1,-5,4] | ||
| <strong>Output:</strong> 6 | ||
| <strong>Explanation:</strong> [4,-1,2,1] has the largest sum = 6. | ||
| </pre> | ||
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| <p><strong>Example 2:</strong></p> | ||
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| <pre><strong>Input:</strong> nums = [1] | ||
| <strong>Output:</strong> 1 | ||
| </pre> | ||
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| <p><strong>Example 3:</strong></p> | ||
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| <pre><strong>Input:</strong> nums = [0] | ||
| <strong>Output:</strong> 0 | ||
| </pre> | ||
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| <p><strong>Example 4:</strong></p> | ||
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| <pre><strong>Input:</strong> nums = [-1] | ||
| <strong>Output:</strong> -1 | ||
| </pre> | ||
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| <p><strong>Example 5:</strong></p> | ||
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| <pre><strong>Input:</strong> nums = [-100000] | ||
| <strong>Output:</strong> -100000 | ||
| </pre> | ||
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| <p> </p> | ||
| <p><strong>Constraints:</strong></p> | ||
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| <ul> | ||
| <li><code>1 <= nums.length <= 3 * 10<sup>4</sup></code></li> | ||
| <li><code>-10<sup>5</sup> <= nums[i] <= 10<sup>5</sup></code></li> | ||
| </ul> | ||
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| <p> </p> | ||
| <strong>Follow up:</strong> If you have figured out the <code>O(n)</code> solution, try coding another solution using the <strong>divide and conquer</strong> approach, which is more subtle.</div> |
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| <div><p>Given an <code>m x n</code> <code>matrix</code>, return <em>all elements of the</em> <code>matrix</code> <em>in spiral order</em>.</p> | ||
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| <p> </p> | ||
| <p><strong>Example 1:</strong></p> | ||
| <img alt="" src="https://assets.leetcode.com/uploads/2020/11/13/spiral1.jpg" style="width: 242px; height: 242px;"> | ||
| <pre><strong>Input:</strong> matrix = [[1,2,3],[4,5,6],[7,8,9]] | ||
| <strong>Output:</strong> [1,2,3,6,9,8,7,4,5] | ||
| </pre> | ||
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| <p><strong>Example 2:</strong></p> | ||
| <img alt="" src="https://assets.leetcode.com/uploads/2020/11/13/spiral.jpg" style="width: 322px; height: 242px;"> | ||
| <pre><strong>Input:</strong> matrix = [[1,2,3,4],[5,6,7,8],[9,10,11,12]] | ||
| <strong>Output:</strong> [1,2,3,4,8,12,11,10,9,5,6,7] | ||
| </pre> | ||
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| <p> </p> | ||
| <p><strong>Constraints:</strong></p> | ||
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| <ul> | ||
| <li><code>m == matrix.length</code></li> | ||
| <li><code>n == matrix[i].length</code></li> | ||
| <li><code>1 <= m, n <= 10</code></li> | ||
| <li><code>-100 <= matrix[i][j] <= 100</code></li> | ||
| </ul> | ||
| </div> |
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| <div><p>Given an array of non-negative integers <code>nums</code>, you are initially positioned at the <strong>first index</strong> of the array.</p> | ||
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| <p>Each element in the array represents your maximum jump length at that position.</p> | ||
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| <p>Determine if you are able to reach the last index.</p> | ||
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| <p> </p> | ||
| <p><strong>Example 1:</strong></p> | ||
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| <pre><strong>Input:</strong> nums = [2,3,1,1,4] | ||
| <strong>Output:</strong> true | ||
| <strong>Explanation:</strong> Jump 1 step from index 0 to 1, then 3 steps to the last index. | ||
| </pre> | ||
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| <p><strong>Example 2:</strong></p> | ||
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| <pre><strong>Input:</strong> nums = [3,2,1,0,4] | ||
| <strong>Output:</strong> false | ||
| <strong>Explanation:</strong> You will always arrive at index 3 no matter what. Its maximum jump length is 0, which makes it impossible to reach the last index. | ||
| </pre> | ||
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| <p> </p> | ||
| <p><strong>Constraints:</strong></p> | ||
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| <ul> | ||
| <li><code>1 <= nums.length <= 3 * 10<sup>4</sup></code></li> | ||
| <li><code>0 <= nums[i] <= 10<sup>5</sup></code></li> | ||
| </ul> | ||
| </div> |
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| <div><p>Given an array of <code>intervals</code> where <code>intervals[i] = [start<sub>i</sub>, end<sub>i</sub>]</code>, merge all overlapping intervals, and return <em>an array of the non-overlapping intervals that cover all the intervals in the input</em>.</p> | ||
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| <p> </p> | ||
| <p><strong>Example 1:</strong></p> | ||
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| <pre><strong>Input:</strong> intervals = [[1,3],[2,6],[8,10],[15,18]] | ||
| <strong>Output:</strong> [[1,6],[8,10],[15,18]] | ||
| <strong>Explanation:</strong> Since intervals [1,3] and [2,6] overlaps, merge them into [1,6]. | ||
| </pre> | ||
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| <p><strong>Example 2:</strong></p> | ||
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| <pre><strong>Input:</strong> intervals = [[1,4],[4,5]] | ||
| <strong>Output:</strong> [[1,5]] | ||
| <strong>Explanation:</strong> Intervals [1,4] and [4,5] are considered overlapping. | ||
| </pre> | ||
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| <p> </p> | ||
| <p><strong>Constraints:</strong></p> | ||
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| <ul> | ||
| <li><code>1 <= intervals.length <= 10<sup>4</sup></code></li> | ||
| <li><code>intervals[i].length == 2</code></li> | ||
| <li><code>0 <= start<sub>i</sub> <= end<sub>i</sub> <= 10<sup>4</sup></code></li> | ||
| </ul> | ||
| </div> |
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| <div><p>Given a set of <em>non-overlapping</em> intervals, insert a new interval into the intervals (merge if necessary).</p> | ||
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| <p>You may assume that the intervals were initially sorted according to their start times.</p> | ||
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| <p> </p> | ||
| <p><strong>Example 1:</strong></p> | ||
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| <pre><strong>Input:</strong> intervals = [[1,3],[6,9]], newInterval = [2,5] | ||
| <strong>Output:</strong> [[1,5],[6,9]] | ||
| </pre> | ||
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| <p><strong>Example 2:</strong></p> | ||
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| <pre><strong>Input:</strong> intervals = [[1,2],[3,5],[6,7],[8,10],[12,16]], newInterval = [4,8] | ||
| <strong>Output:</strong> [[1,2],[3,10],[12,16]] | ||
| <strong>Explanation:</strong> Because the new interval <code>[4,8]</code> overlaps with <code>[3,5],[6,7],[8,10]</code>.</pre> | ||
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| <p><strong>Example 3:</strong></p> | ||
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| <pre><strong>Input:</strong> intervals = [], newInterval = [5,7] | ||
| <strong>Output:</strong> [[5,7]] | ||
| </pre> | ||
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| <p><strong>Example 4:</strong></p> | ||
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| <pre><strong>Input:</strong> intervals = [[1,5]], newInterval = [2,3] | ||
| <strong>Output:</strong> [[1,5]] | ||
| </pre> | ||
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| <p><strong>Example 5:</strong></p> | ||
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| <pre><strong>Input:</strong> intervals = [[1,5]], newInterval = [2,7] | ||
| <strong>Output:</strong> [[1,7]] | ||
| </pre> | ||
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| <p> </p> | ||
| <p><strong>Constraints:</strong></p> | ||
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| <ul> | ||
| <li><code>0 <= intervals.length <= 10<sup>4</sup></code></li> | ||
| <li><code>intervals[i].length == 2</code></li> | ||
| <li><code>0 <= intervals[i][0] <= intervals[i][1] <= 10<sup>5</sup></code></li> | ||
| <li><code>intervals</code> is sorted by <code>intervals[i][0]</code> in <strong>ascending</strong> order.</li> | ||
| <li><code>newInterval.length == 2</code></li> | ||
| <li><code>0 <= newInterval[0] <= newInterval[1] <= 10<sup>5</sup></code></li> | ||
| </ul> | ||
| </div> |
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| <div><p>Given a string <code>s</code> consists of some words separated by spaces, return <em>the length of the last word in the string. If the last word does not exist, return </em><code>0</code>.</p> | ||
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| <p>A <strong>word</strong> is a maximal substring consisting of non-space characters only.</p> | ||
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| <p> </p> | ||
| <p><strong>Example 1:</strong></p> | ||
| <pre><strong>Input:</strong> s = "Hello World" | ||
| <strong>Output:</strong> 5 | ||
| </pre><p><strong>Example 2:</strong></p> | ||
| <pre><strong>Input:</strong> s = " " | ||
| <strong>Output:</strong> 0 | ||
| </pre> | ||
| <p> </p> | ||
| <p><strong>Constraints:</strong></p> | ||
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| <ul> | ||
| <li><code>1 <= s.length <= 10<sup>4</sup></code></li> | ||
| <li><code>s</code> consists of only English letters and spaces <code>' '</code>.</li> | ||
| </ul> | ||
| </div> |
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| <div><p>Given a positive integer <code>n</code>, generate an <code>n x n</code> <code>matrix</code> filled with elements from <code>1</code> to <code>n<sup>2</sup></code> in spiral order.</p> | ||
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| <p> </p> | ||
| <p><strong>Example 1:</strong></p> | ||
| <img alt="" src="https://assets.leetcode.com/uploads/2020/11/13/spiraln.jpg" style="width: 242px; height: 242px;"> | ||
| <pre><strong>Input:</strong> n = 3 | ||
| <strong>Output:</strong> [[1,2,3],[8,9,4],[7,6,5]] | ||
| </pre> | ||
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| <p><strong>Example 2:</strong></p> | ||
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| <pre><strong>Input:</strong> n = 1 | ||
| <strong>Output:</strong> [[1]] | ||
| </pre> | ||
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| <p> </p> | ||
| <p><strong>Constraints:</strong></p> | ||
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| <ul> | ||
| <li><code>1 <= n <= 20</code></li> | ||
| </ul> | ||
| </div> |
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| <div><p>The set <code>[1, 2, 3, ..., n]</code> contains a total of <code>n!</code> unique permutations.</p> | ||
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| <p>By listing and labeling all of the permutations in order, we get the following sequence for <code>n = 3</code>:</p> | ||
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| <ol> | ||
| <li><code>"123"</code></li> | ||
| <li><code>"132"</code></li> | ||
| <li><code>"213"</code></li> | ||
| <li><code>"231"</code></li> | ||
| <li><code>"312"</code></li> | ||
| <li><code>"321"</code></li> | ||
| </ol> | ||
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| <p>Given <code>n</code> and <code>k</code>, return the <code>k<sup>th</sup></code> permutation sequence.</p> | ||
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| <p> </p> | ||
| <p><strong>Example 1:</strong></p> | ||
| <pre><strong>Input:</strong> n = 3, k = 3 | ||
| <strong>Output:</strong> "213" | ||
| </pre><p><strong>Example 2:</strong></p> | ||
| <pre><strong>Input:</strong> n = 4, k = 9 | ||
| <strong>Output:</strong> "2314" | ||
| </pre><p><strong>Example 3:</strong></p> | ||
| <pre><strong>Input:</strong> n = 3, k = 1 | ||
| <strong>Output:</strong> "123" | ||
| </pre> | ||
| <p> </p> | ||
| <p><strong>Constraints:</strong></p> | ||
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| <ul> | ||
| <li><code>1 <= n <= 9</code></li> | ||
| <li><code>1 <= k <= n!</code></li> | ||
| </ul> | ||
| </div> |
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| <div><p>Given the <code>head</code> of a linked list, rotate the list to the right by <code>k</code> places.</p> | ||
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| <p> </p> | ||
| <p><strong>Example 1:</strong></p> | ||
| <img alt="" src="https://assets.leetcode.com/uploads/2020/11/13/rotate1.jpg" style="width: 600px; height: 254px;"> | ||
| <pre><strong>Input:</strong> head = [1,2,3,4,5], k = 2 | ||
| <strong>Output:</strong> [4,5,1,2,3] | ||
| </pre> | ||
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| <p><strong>Example 2:</strong></p> | ||
| <img alt="" src="https://assets.leetcode.com/uploads/2020/11/13/roate2.jpg" style="width: 472px; height: 542px;"> | ||
| <pre><strong>Input:</strong> head = [0,1,2], k = 4 | ||
| <strong>Output:</strong> [2,0,1] | ||
| </pre> | ||
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| <p> </p> | ||
| <p><strong>Constraints:</strong></p> | ||
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| <ul> | ||
| <li>The number of nodes in the list is in the range <code>[0, 500]</code>.</li> | ||
| <li><code>-100 <= Node.val <= 100</code></li> | ||
| <li><code>0 <= k <= 2 * 10<sup>9</sup></code></li> | ||
| </ul> | ||
| </div> |
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| <div><p>A robot is located at the top-left corner of a <code>m x n</code> grid (marked 'Start' in the diagram below).</p> | ||
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| <p>The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid (marked 'Finish' in the diagram below).</p> | ||
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| <p>How many possible unique paths are there?</p> | ||
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| <p> </p> | ||
| <p><strong>Example 1:</strong></p> | ||
| <img src="https://assets.leetcode.com/uploads/2018/10/22/robot_maze.png" style="width: 400px; height: 183px;"> | ||
| <pre><strong>Input:</strong> m = 3, n = 7 | ||
| <strong>Output:</strong> 28 | ||
| </pre> | ||
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| <p><strong>Example 2:</strong></p> | ||
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| <pre><strong>Input:</strong> m = 3, n = 2 | ||
| <strong>Output:</strong> 3 | ||
| <strong>Explanation:</strong> | ||
| From the top-left corner, there are a total of 3 ways to reach the bottom-right corner: | ||
| 1. Right -> Down -> Down | ||
| 2. Down -> Down -> Right | ||
| 3. Down -> Right -> Down | ||
| </pre> | ||
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| <p><strong>Example 3:</strong></p> | ||
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| <pre><strong>Input:</strong> m = 7, n = 3 | ||
| <strong>Output:</strong> 28 | ||
| </pre> | ||
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| <p><strong>Example 4:</strong></p> | ||
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| <pre><strong>Input:</strong> m = 3, n = 3 | ||
| <strong>Output:</strong> 6 | ||
| </pre> | ||
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| <p> </p> | ||
| <p><strong>Constraints:</strong></p> | ||
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| <ul> | ||
| <li><code>1 <= m, n <= 100</code></li> | ||
| <li>It's guaranteed that the answer will be less than or equal to <code>2 * 10<sup>9</sup></code>.</li> | ||
| </ul> | ||
| </div> |
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