Description
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.
Note: A leaf is a node with no children.
Example:
Given binary tree [3,9,20,null,null,15,7]
,
3
/
9 20
/
15 7
return its depth = 3.
Analyse
计算二叉树的高度,很基础的问题
两种思路:递归和层序遍历
层序遍历的时候需要一个queue辅助,每次进while循环的时候queue里是树的一层的节点,出队列后将下一层的节点入队列,需要记录每一层有几个节点来区分不同层的节点
int maxDepth(TreeNode* root) {
if (!root) return 0;
queue<TreeNode*> que;
que.push(root);
int depth = 0;
while (!que.empty())
{
int layer_count = que.size();
for (int i = 0; i < layer_count; ++i)
{
TreeNode* tmp = que.front();
que.pop();
if (tmp->left) { que.push(tmp->left); }
if (tmp->right) { que.push(tmp->right); }
}
++depth;
}
return depth;
}
更好的办法是用递归做,但我没想到,贴一个leetcode上大佬的代码,递归两行解决问题,递归也太强了
int maxDepth(TreeNode* root)
{
if(root==NULL){return 0;}
return max(maxDepth(root->left), maxDepth(root->right)) + 1;
}