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.

分析：此题跟maximum depth of binary tree相似，但要注意的是minimum depth的定义，如果根节点的某个孩子为null，我们将不考虑该孩子的高度因为minimum depth定义是根到叶子节点的最短路径上的节点数。代码如下：

class Solution {
public:
    int minDepth(TreeNode *root) {
        if(root == NULL) return 0;
        
        int left_depth = minDepth(root->left);
        int right_depth = minDepth(root->right);
        
        if(left_depth == 0) return right_depth + 1;
        if(right_depth == 0) return left_depth + 1;
        
        return min(right_depth, left_depth) + 1;
    }
};