2173: Sum in Set

2173: Sum in Set

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Result	TIME Limit	MEMORY Limit	Run Times	AC Times	JUDGE
	3s	32768K	1401	235	Standard

In this problem you will be given a set (S) of numbers. Your task is to check whether there are three numbers in S, called A, B, C, such that A+B+C=0. (A, B, C may be the same number)

Input

There are more than one test cases in the input file. Each test case contains two lines. The first line have just one positive integer N (1 <= N <= 1000). The second line have N numbers seperated by spaces. The last case contains N=0 which you should not process.

Output

For each test case just print "yes" if there are A+B+C=0 or "no" if there are not.

Sample Input

5
0 1 2 3 4
3
-1 2 4
2
1 2
0

Sample Output

yes
yes
no

 

Problem Source: coldcpp

#include<stdio.h>
#include<stdlib.h>
int cmp(const void *a,const void *b)
{ return *(double *)a-*(double *)b;}
int main()
{ double a[1000];
int n;
while(scanf("%d",&n)!=EOF)
 {  
 if(n==0) 
  break;
 int i,temp;  
 for(i=0;i<n;i++)
  scanf("%lf",&a[i]);
 qsort(a,n,sizeof(a[0]),cmp);
 int head,tail; 
 bool flag=false; 
 for(i=0;i<n;i++)  
 {    temp=a[i]; 
 head=0;    
 tail=n-1;  
 while(head<=tail)
    {   
  if((temp+a[head]+a[tail])==0)    
  {      flag=true;      break; 
   }  
  else if(temp+a[head]+a[tail]<0) 
   head++;   
  else tail--; 
  }   
 if(flag) 
  break; 
 } 
 if(flag) 
  printf("yes/n"); 
 else printf("no/n");
 }
return 0;
}