3 - 二叉树的最大深度
104. 二叉树的最大深度
算法1：递归写法
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
int maxDepth(TreeNode* root) {
if(!root) return 0;
int left = maxDepth(root->left);
int right = maxDepth(root->right);
return max(left,right) + 1;
}
};
算法2：非递归算法
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
int maxDepth(TreeNode* root) {
if(!root) return 0;
queue<TreeNode*> q;
q.push(root);
int level = 0;
while(q.size())
{
int n = q.size();
while(n--)
{
auto t = q.front();
q.pop();
if(t->left) q.push(t->left);
if(t->right) q.push(t->right);
}
level ++;
}
return level;
}
};