leetcode 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.

就是对树进行遍历，每次深度+1，当左右节点都为空的时候表示到达了叶节点，比较如果比当前的min小，则记录。

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:void dfs(TreeNode* root, int &min, int dep){if (root == NULL) return;if (root->left == NULL && root->right == NULL){if (min > dep) min = dep;return;}dfs(root->left, min, dep + 1);dfs(root->right, min, dep + 1);}int minDepth(TreeNode* root) {    if (!root) return 0;int min = 9999;dfs(root, min, 1);return min;}};