力扣第62题：不同路径

62. 不同路径 - 力扣（LeetCode）

class Solution {public int uniquePaths(int m, int n) {int[][] array = new int[m][n];for(int i = 0;i<n;i++){array[0][i] = 1;}for(int i = 0;i<m;i++){array[i][0] = 1;}for(int i = 1;i<m;i++){for(int j =1;j<n;j++ ){array[i][j] = array[i - 1][j] + array[i] [j-1];}}return array[m -1] [ n - 1];}}

力扣第64题：最小路径和

64. 最小路径和 - 力扣（LeetCode）

class Solution {public int minPathSum(int[][] grid) {int[][] array= new int[grid.length][grid[0].length];array[0][0] = grid[0][0];//行for(int i = 1;i<grid[0].length;i++){array[0][i] = array[0][i -1] + grid[0][i];}//列for(int i = 1;i<grid.length;i++){array[i][0] = array[i - 1][0] + grid[i][0];}for(int i = 1;i<grid.length;i++){for(int j = 1;j<grid[0].length;j++){array[i][j] = Math.min(array[i - 1][j] ,array[i][j - 1]) + grid[i][j];}}return array[grid.length - 1][grid[0].length - 1];}
}

力扣第287题:寻找重复数

287. 寻找重复数 - 力扣（LeetCode）

class Solution {public int findDuplicate(int[] nums) {HashMap<Integer,Integer> map = new HashMap<>();for(int num: nums){if(map.containsKey(num)){return num;}map.put(num,1);}return - 1;}
}

力扣第108题：将有序数组转换为二叉搜索树

108. 将有序数组转换为二叉搜索树 - 力扣（LeetCode）

/*** Definition for a binary tree node.* public class TreeNode {*     int val;*     TreeNode left;*     TreeNode right;*     TreeNode() {}*     TreeNode(int val) { this.val = val; }*     TreeNode(int val, TreeNode left, TreeNode right) {*         this.val = val;*         this.left = left;*         this.right = right;*     }* }*/
class Solution {public TreeNode sortedArrayToBST(int[] nums) {return helper(nums,0,nums.length - 1);}private TreeNode helper(int nums[],int left,int right){if(left > right){return null;}int mid = (left + right) /2;TreeNode s = new TreeNode(nums[mid]);s.left = helper(nums,left,mid-1);s.right = helper(nums,mid + 1,right);return s;}
}

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