poj2549——Sumsets

#include<iostream>
#include<string>
#include<cstdio>
#include<algorithm>
using namespace std;
#define N 1005
int maxsum,n;
bool flag;
bool search(int left,int right,int key,int k1,int k2,int b[])
{
int mid;
while(left<=right)
{
int mid=(left+right)>>1;
if(b[mid]==key&&mid!=k1&&mid!=k2) return true;
if(b[mid]>key)
right=mid-1;
else if(b[mid]<key)left=mid+1;
}
return false;
}
int main()
{
int i,a
,j,k;
while(scanf("%d",&n)&&n)
{
flag=false;
for(i=1;i<=n;i++)
scanf("%d",&a[i]);
if(n<3)
cout<<"no solution"<<endl;
else
{
maxsum=-999999999;
sort(a+1,a+1+n);
int b
;
int cnt=1;i=1;
while(i<=n)
{
b[cnt++]=a[i];
int k=i;
while(i<=n&&a[k]==a[i])
i++;
}
for(k=cnt-1;k>=1;k--)
{
maxsum=b[k];
for(i=cnt-1;i>=1;i--)
{
if(k==i) continue;
if(b[i]+b[0]+b[1]>maxsum) continue;
for(j=i-1;j>=1;j--)
{
if(j==i||j==k) continue;
if(search(1,j-1,maxsum-b[i]-b[j],k,i,b))
{
flag=true;
goto end;
}
}
}
}
end:
if(flag)
cout<<maxsum<<endl;
else cout<<"no solution"<<endl;
}
}
return 0;
}