[LeetCode] Maximum Depth of Binary Tree

Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

这道题非常直接，只需要递归深搜就可以。需要注意的是递归的终止条件：root为空，深度为0；root没有孩子，深度为1。如果存在孩子，则递归深搜下去。

/**

 * Definition for binary tree

 * struct TreeNode {

 *     int val;

 *     TreeNode *left;

 *     TreeNode *right;

 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}

 * };

 */

class Solution {

public:

    int maxDepth(TreeNode *root) {

        // IMPORTANT: Please reset any member data you declared, as

        // the same Solution instance will be reused for each test case.

        if(root == NULL)

            return 0;

        

        if(root -> left == NULL && root -> right == NULL)

            return 1;

        

        int leftDepth = 0, rightDepth = 0;

        if(root -> left != NULL)

            leftDepth = maxDepth(root -> left) + 1;

        if(root -> right != NULL)

            rightDepth = maxDepth(root -> right) + 1;

        

        return (leftDepth > rightDepth) ? leftDepth : rightDepth;

        

    }

    

};

写完后看了博客园另一位博主的写法，发现自己的第一个if其实只是为了填补后面写的代码的漏洞，这个问题完全可以用精简得多的方式写出来。/ * Definition for binary tree

 * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ class Solution { public: int maxDepth(TreeNode *root) { // Start typing your C/C++ solution below // DO NOT write int main() function if (root == NULL) return 0; return max(maxDepth(root->left),maxDepth(root->right)) + 1; } };