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);
}
};