【LeetCode】104. Maximum Depth of Binary Tree 解法及注释，递归，深度搜索

104. Maximum Depth of Binary Tree

Total
Accepted: 137961 Total
Submissions: 289093 Difficulty: Easy

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.

【分析】

这个题很简单，就是一个搜索问题，对二叉树进行遍历并记录最大深度即可解决问题，我用的是中序遍历，当然其它遍历也可解决问题。遍历的思路如是，代码的书写风格亦会影响效率，从提高扩展性的角度看，选择一种中序遍历是不错的，作为独立函数执行效率尚可。

【解法及注释】

方法一：递归遍历所有结点，记录最大深度

class Solution {
public:
int maxDepth(TreeNode* root)
{
int maxdeep=0;
DFS(root, 0, maxdeep);
return maxdeep;
}

void DFS(TreeNode* root, int deepth,int &maxdeep)
{
if(root==NULL)return;
if(deepth+1>maxdeep)maxdeep=deepth+1;
DFS(root->left,deepth+1,maxdeep);
DFS(root->right,deepth+1,maxdeep);
}
};

方法二：网上解法，效率不高

class Solution {
public:
int maxDepth(TreeNode *root) {
if (root == NULL) return 0;
TreeNode* left_node = root->left;
TreeNode* right_node = root->right;
int left_dep = maxDepth(left_node);
int right_dep = maxDepth(right_node);
return 1 + ((left_dep > right_dep) ? left_dep:right_dep);
}
};