Maximum Depth of Binary Tree leetcode

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.

Anwser 1 ：  DFS

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

Anwser 2 ：    BFS   in  queue

class Solution {
public:
int maxDepth(TreeNode *root) {
if(root == NULL)
return 0;
queue<TreeNode*> q;
q.push(root);
int count = 1;
int depth = 0;
while(!q.empty()) {
TreeNode* tmp = q.front();
q.pop();
count--;
if(tmp->left != NULL)
q.push(tmp->left);
if(tmp->right != NULL)
q.push(tmp->right);
if(count == 0) {
depth++;
count = q.size();
}
}
return depth;
}
};

Minimum Depth of Binary Tree

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.
递归：
class Solution {
public:
int minDepth(TreeNode *root) {
if(root == NULL)
return 0;
int left = minDepth(root->left);
int right = minDepth(root->right);
if(left*right != 0)
return (left<right? left:right)+1;
if(left == 0)
return right+1;
if(right == 0)
return left+1;
}
};