leetcode:Maximum Depth of Binary Tree

使用层遍历法计算二叉树的调试
/**
 * 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)
	{
		int depth=0;
		if(root==NULL)
			return 0;
		vector<TreeNode *>vec;
		vec.push_back(root);
		int cur=0;
		int last=1;
		while(cur<vec.size())
		{
			last=vec.size();
			while(cur<last)
			{
				if(vec[cur]->left)
					vec.push_back(vec[cur]->left);
				if(vec[cur]->right)
					vec.push_back(vec[cur]->right);
				++cur;
			}
			++depth;
		} 
		return depth;
	}
｝;

　　

使用队列计算二叉树调试，在队列中加入一个结束符号NULL,即在每一行结束处加入NULL，在遍历的过程中，遇到NULL深度增加，当队列为空时结束搜索

class Solution{
public:
	int maxDepth(TreeNode *root)
	{
		if(root==NULL)
			return 0;
		int depth=0;
		queue<TreeNode*> q;
		TreeNode *p;
		q.push(root);
		q.push(NULL);
		while(true)
		{
			p=q.front();
			q.pop();
			if(p)
			{
				if(p->left)
					q.push(p->left);
				if(p->right)
					q.push(p->right);
			}
			else
			{
				++depth;
				if(q.empty())
				    break;
				q.push(NULL);
			}
		}
		return depth;
	}
};