Traveling 【图的性质】

Traveling

时间限制: 1 Sec 内存限制: 32 MB

提交: 41 解决: 23

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题目描述

SH likes traveling around the world. When he arrives at a city, he will ask the staff about the number of cities that connected with this city directly. After traveling around a mainland, SH will collate data and judge whether the data is correct.

A group of data is correct when it can constitute an undirected graph.

输入

There are multiple test cases. The first line of each test case is a positive integer N (1<=N<=10000) standing for the number of cities in a mainland. The second line has N positive integers a1, a2, …,an. ai stands for the number of cities that connected directly with the ith city. Input will be ended by the END OF FILE.

输出

If a group of data is correct, output “YES” in one line, otherwise, output “NO”.

样例输入

8

7 7 4 3 3 3 2 1

10

5 4 3 3 2 2 2 1 1 1

样例输出

NO

YES

#include <stdio.h>
#include <iostream>
#include <string.h>
#include <algorithm>
#include <math.h>
#include <ctype.h>
#include <time.h>
#include <queue>

using namespace std;

const int MAXN =10010;

int p[MAXN];
int n;

int solve ()
{
    for(int i=0;i<n;i++)
    {
        for(int j=i+1;j<n;j++)
        {
            if (p[i]>0 && p[j] >0)
            {
                p[i]-- ;
                p[j]--;
            }
        }
        if (p[i]!=0)
        {
            return 0;
        }
    }
    return 1;
}

int main()
{
    while (scanf("%d",&n)!=EOF)
    {
        for(int i=0;i<n;i++)
            scanf("%d",&p[i]);
        if (solve())
            printf("YES\n");
        else
            printf("NO\n");
    }
    return 0;
}