111. 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.

题意:

求二叉树的最小深度

思路：

求二叉树的最小深度，用经典的递归算法。注意：最小深度必须是从根节点到叶子节点。如果一个结点只有一个子树，深度要以有子树一边为准为准。

/** * 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) {        if (root == NULL) return 0;        if (root->left == NULL && root->right == NULL) return 1;        if (root->left == NULL) return minDepth(root->right) + 1;        else if (root->right == NULL) return minDepth(root->left) + 1;        else return 1 + min(minDepth(root->left), minDepth(root->right));    }};