37.二叉树的最大深度

1.递归的理解

2.代码

class Solution {
public:
    int maxDepth(TreeNode* root) {
        if(root==NULL){
            return 0;
        }
        int leftdepth = maxDepth(root->left);
        int rightdepth = maxDepth(root->right);
        int realdepth = max(leftdepth,rightdepth)+1;//1为根节点
        return realdepth;
    }
};