LeetCode Binary Tree Level Order Traversal

最新推荐文章于 2025-09-18 03:57:00 发布

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本文介绍了一种特殊的二叉树层次遍历方法，通过为每个节点分配唯一编号来区分不同层级，确保正确地按层输出节点值。使用C++实现，并提供了具体的代码示例。

这题不是普通的层次遍历，而且要分清每一层，办法就是对每一层的节点标注编号，编号相同的在同一层，队列里的元素是经过编号后的新结构体，刚开始想用1,2,4,8来编号这样能表示所有的节点，但是当层数多的时候数字不够用了，所以只能用012345678来编号了。如下：

// LeetCode_BinaryTreeLevelOrderTraversal.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <iostream>
#include <vector>
#include <queue>
using namespace std;

struct TreeNode {
	     int val;
	     TreeNode *left;
	     TreeNode *right;
	     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
	 };
struct QueNode{
	int num;
	TreeNode *pTreeNode;
	QueNode():num(0),pTreeNode(NULL){}
};
vector<vector<int> > levelOrder(TreeNode *root) {
	vector<vector<int> >ret;
	vector<int> oneresult;
	if(root==NULL)
		return ret;
	queue<QueNode> que;
	QueNode qn;
	qn.num = 0;
	qn.pTreeNode = root;
	que.push(qn);
	QueNode tempNode,tempLeftNode,tempRightNode;
	int lastnum = 0;
	while(!que.empty())
	{
		tempNode = que.front();
		que.pop();
		if (lastnum!=tempNode.num)
		{
			ret.push_back(oneresult);
			oneresult.clear();
			oneresult.push_back(tempNode.pTreeNode->val);
			lastnum = tempNode.num;
		}
		else
			oneresult.push_back(tempNode.pTreeNode->val);
		if (tempNode.pTreeNode->left)
		{
			tempLeftNode.num = tempNode.num+1;
			tempLeftNode.pTreeNode = tempNode.pTreeNode->left;
			que.push(tempLeftNode);
		}
		if (tempNode.pTreeNode->right)
		{
			tempRightNode.num = tempNode.num+1;
			tempRightNode.pTreeNode = tempNode.pTreeNode->right;
			que.push(tempRightNode);
		}	
	}
	ret.push_back(oneresult);
	oneresult.clear();
	return ret;
}

int _tmain(int argc, _TCHAR* argv[])
{
	TreeNode *pa = new TreeNode(1);
	TreeNode *pb = new TreeNode(2);
	TreeNode *pc = new TreeNode(2);
	TreeNode *pd = new TreeNode(3);//TreeNode *pd = NULL;//
	TreeNode *pe = new TreeNode(4);
	TreeNode *pf = NULL;//TreeNode *pf = new TreeNode(3);
	TreeNode *pg = new TreeNode(3);
	pa->left = pb;
	pa->right = pc;
	pb->left = pd;
	pb->right = pe;
	pc->left = pf;
	pc->right = pg;
	vector<vector<int> >ret;
	ret = levelOrder(pa);
	system("pause");
	return 0;
}