#include <iostream>
using namespace std;


long long a,n,w[25],c,s,b;
int main()
{
   cin >>n;
   a=1;  w[0]=0;
   for ( ;a<=n;a++)
      cin >>w[a];
   a=1;
   if (n==1) cout <<w[1]<<"\n"; else
   {
     for ( ;a<=n;a++)
     {
         s=a;
         for ( s;s<=n-1;s++)
           {
             if (w[a]>w[s+1]) { c=w[a]; w[a]=w[s+1]; w[s+1]=c;};
           }
     }
     a=n;
     for ( ;a>=3;a--)
       {
         w[a-1]=w[a]-w[a-1];
         if (w[a-2]>w[a-1]) {c=w[a-2]; w[a-2]=w[a-1]; w[a-1]=c;};
       }
     cout <<w[2]-w[1]<<"\n";
   }

   return 0;
}

You solve is very big.
My solve get WA5, but my solve if less.
on C:
#include <stdio.h>
void main()
{
int n,i,j;
__int64 w[21],s1=0,s2=0;
scanf("%d",&n);
for(i=0;i<n;++i)scanf("%I64d",&w[i]);
for(i=0;i<n-1;++i)for(j=i+1;j<n;++j)
  if(w[i]<w[j]){int t=w[i];w[i]=w[j]; w[j]=t;};
s1=w[0];
for(i=1;i<n;++i)
  if(s1<s2)s1+=w[i];
  else s2+=w[i];
if(s1>s2)s1-=s2;
else s1=s2-s1;
printf("%I64d",s1);
}

Both solution is wrang. Try full search.