LeetCode111. Minimum Depth of Binary Tree

LeetCode111.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.

由题意，要寻找该二叉树的最小深度值，即要找到最近的那个叶子节点。假若用DFS，要不停搜寻、排错，而用BFS，一圈圈那样扩展下去，找到第一个子节点即可停止，因此要方便适合得多。

代码如下：

/** * 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:    int minDepth(TreeNode* root) {        if (root == NULL) return 0;        int left_minDepth = minDepth(root->left);        int right_minDepth = minDepth(root->right);        if (left_minDepth == 0) return right_minDepth + 1;        if (right_minDepth == 0) return left_minDepth + 1;        return left_minDepth > right_minDepth?right_minDepth + 1:left_minDepth + 1;    }};