leetcode 31: Minimum Depth of Binary Tree

Given 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.

1. different from maximum depth. if a node only has one child, the depth will be 1 + child depth.

public class Solution {    public int minDepth(TreeNode root) {        if(root==null) return 0;                if(root.left==null) return minDepth(root.right)+1;        if(root.right==null) return minDepth(root.left)+1;        return Math.min(minDepth(root.right), minDepth(root.left)) + 1;    }}

 * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    int minDepth(TreeNode *root) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        return minRec(root);    }        int minRec( TreeNode * root) {        if(!root) return 0;                int left = minRec( root->left);        int right = minRec( root->right);                if(left && right) return 1 + min(left, right);        if(left || right) return 1+left+right;        return 1;    }};

/** * Definition for binary tree * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public int minDepth(TreeNode root) {        // Start typing your Java solution below        // DO NOT write main() function        return minRec(root);    }        private int minRec(TreeNode root) {        if(root==null) return 0;                int l = minRec(root.left);        int r = minRec(root.right);                if(l==0) return r+1;        if(r==0) return l+1;                return Math.min(l, r) + 1;            }}