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.
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.
If a group of data is correct, output "YES" in one line, otherwise, output "NO".
8 7 7 4 3 3 3 2 1 10 5 4 3 3 2 2 2 1 1 1
NO YES
上代码
#include<stdio.h> int a[12345]; int main(){ int n,i,j,flag; while(~scanf("%d",&n)) { flag=1; for(i=0;i<n;i++) scanf("%d",&a[i]); for(i=0;i<n;i++) { for(j=i+1;j<n;j++) { if(a[i]&&a[j]){ a[i]--; a[j]--; } } if(a[i]!=0) { printf("NO\n"); flag=0; break; } } if(flag) printf("YES\n"); } return 0; } /************************************************************** Problem: 10 User: Hui Language: C Result: Accepted Time:100 ms Memory:1012 kb ****************************************************************/
原文地址：http://www.cnblogs.com/suthui/p/3816305.html
