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.

class Solution {public:    int minDepth(TreeNode *root) {        if(root == NULL) return 0;        int left = minDepth(root->left);        int right = minDepth(root->right);        if(!root->left || !root->right)        return (left < right ? right : left) + 1;        else         return (left < right ? left : right) + 1;    }};

结点的某个孩子结点为空的时候，那么经由该空孩子肯定到达不了叶子结点，那么只能是返回较大值了，当左右都可达时，那就返回较小值了。