LeetCode-MinimumDepthOfBinaryTree

题目:

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.

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */

分析:
查找二叉树的最小深度
分2种情况:
如果结点为NULL,返回0
否则,返回1+左右结点的最小深度
但这里有个地方需要注意,如果左右结点有一个为空,则应该返回1+另一个不为空的深度
如果左右节点都为空直接返回1
总结一下就是

if(l==0 || r==0)
    return 1+l+r;

AC代码

class Solution {
public:
    int minDepth(TreeNode* root) {
        if(!root)
            return 0;
        int l = minDepth(root->left);
        int r = minDepth(root->right);
        if(l==0 || r==0)
            return 1+l+r;
        return 1+min(l,r);
    }
};