Alan 的筆記本

200. Number of Islands https://leetcode.com/problems/number-of-islands/ MediumGiven an m x n 2D binary grid grid which represents a map of '1's (land) and '0's (water), return the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.   Example 1: Input: grid = [ ["1","1","1","1","0"], ["1","1","0","1","0"], ["1","1","0","0","0"], ["0","0","0","0","0"]

78. Subsets https://leetcode.com/problems/subsets/ MediumGiven an integer array nums of unique elements, return all possible subsets (the power set). The solution set must not contain duplicate subsets. Return the solution in any order.   Example 1: Input: nums = [1,2,3] Output: [[],[1],[2],[1,2],[3],[1,3],[2,3],[1,2,3]] Example 2: Input: nums = [0] Output: [[],[0]]   Constraints: 1 <= nums.length <= 10 -10 <= nums[i] <= 10 All the numbers of nums are unique. 題意 傳

111. Minimum Depth of Binary Tree https://leetcode.com/problems/minimum-depth-of-binary-tree/ EasyGiven a binary tree, find its minimum depth. The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node. Note: A leaf is a node with no children.   Example 1: Input: root = [3,9,20,null,null,15,7] Output: 2 Example 2: Input: root = [2,null,3,null,4,null,5,null,6] Output: 5   Constraints: The number of nodes in the

104. Maximum Depth of Binary Tree https://leetcode.com/problems/maximum-depth-of-binary-tree/ EasyGiven the root of a binary tree, return its maximum depth. A binary tree's maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.   Example 1: Input: root = [3,9,20,null,null,15,7] Output: 3 Example 2: Input: root = [1,null,2] Output: 2   Constraints: The number of nodes in the tree is in the

226. Invert Binary Tree https://leetcode.com/problems/invert-binary-tree/ EasyGiven the root of a binary tree, invert the tree, and return its root.   Example 1: Input: root = [4,2,7,1,3,6,9] Output: [4,7,2,9,6,3,1] Example 2: Input: root = [2,1,3] Output: [2,3,1] Example 3: Input: root = [] Output: []   Constraints: The number of nodes in the tree is in the range [0, 100]. -100 <= Node.val <= 100 題意 將整棵樹