List Leaves【建立树，层序遍历】

最新推荐文章于 2021-06-27 21:52:42 发布

原创最新推荐文章于 2021-06-27 21:52:42 发布 · 300 阅读

0 ·

CC 4.0 BY-SA版权

数据结构与算法同时被 2 个专栏收录

76 篇文章

订阅专栏

树

29 篇文章

订阅专栏

给定一棵树，任务是按照自顶向下、从左到右的顺序列出所有叶子节点的索引。输入包含一棵最多10个节点的树，每个节点的左右子节点索引以空格分隔，不存在的子节点用'-'表示。

7-4 List Leaves (25分)
Given a tree, you are supposed to list all the leaves in the order of top down, and left to right.

Input Specification:
Each input file contains one test case. For each case, the first line gives a positive integer N (≤10) which is the total number of nodes in the tree – and hence the nodes are numbered from 0 to N−1. Then N lines follow, each corresponds to a node, and gives the indices of the left and right children of the node. If the child does not exist, a “-” will be put at the position. Any pair of children are separated by a space.

Output Specification:
For each test case, print in one line all the leaves’ indices in the order of top down, and left to right. There must be exactly one space between any adjacent numbers, and no extra space at the end of the line.
在这里插入图片描述

#include<iostream>
#include<queue>
using namespace std;
#define MAX 10

struct Node
{
	int left,right;
}T[MAX];

int buildTree(struct Node T[],int n)
{
	if(n==0) return -1;
	int i,flag[n];
	for(i=0;i<n;i++)
	{
		flag[i]=0;
	}
	
	char cl,cr;
	for(i=0;i<n;i++)
	{
		cin>>cl>>cr;
		
		if(cl!='-')
		{
			T[i].left=cl-'0';
			flag[T[i].left]=1;
		}
		else T[i].left=-1;
		if(cr!='-')
		{
			T[i].right=cr-'0';
			flag[T[i].right]=1;
		}
		else T[i].right=-1;
	}
	for(int i=0;i<n;i++)
		if(flag[i]==0) return i;
}

void findLeaves(int t,queue<int>&Queue,int Leaves[],int* pj)  //层序遍历找叶子 
{
	//cout<<"层序遍历："; 
	Queue.push(t);
	int node;
	while(Queue.size())
	{
		node=Queue.front();
		Queue.pop();
		if(T[node].left==-1&&T[node].right==-1) Leaves[(*pj)++]=node;
		if(T[node].left!=-1)
			Queue.push(T[node].left);
		if(T[node].right!=-1)
			Queue.push(T[node].right);
	}
}

int main()
{
	int n,i;
	cin>>n;
	int t;
	t=buildTree(T,n);
	//cout<<"root="<<t<<endl;
	
	int Leaves[n],j=0;
	queue<int> Queue;
	for(i=0;i<n;i++) Leaves[i]=0;
	findLeaves(t,Queue,Leaves,&j);
	//cout<<"j="<<j<<endl;
	
	int flag=0;
	for(i=0;i<j;i++)
	{
		if(flag==0) flag=1;
		else cout<<" ";
		cout<<Leaves[i];
	}
	
	return 0;
}