program correctly solves all problems, but for some reason the site shows that the program is wrong ... can you explain why?

#include<iostream>
using namespace std;

int main()
{
    double ves_k[20];
    int i,num;
    double t,perv,vtor,res;

    cin>>num;
    if(num<1||num>20) goto vozvrat;
    for(i=0; i<num; i++){
        cin>>ves_k[i];
        if(ves_k[i]<1||ves_k[i]>10000) goto vozvrat;
    }
    if(num!=1){
    for(int a=1; a<i; a++)
        for(int b=i-1; b>=a; b--){
            if(ves_k[b-1]>ves_k[b]) {
                t=ves_k[b-1];
                ves_k[b-1]=ves_k[b];
                ves_k[b]=t;
            }
        }
    perv=ves_k[num-1];
    vtor=ves_k[num-2];
    for(i=num-3; i>=0; i--){
        if(perv>=vtor) vtor+=ves_k[i];
        else perv+=ves_k[i];
    }
    res=perv-vtor;
    if(res<0) res=-res;
    } else res=ves_k[0];

    cout<<res;
vozvrat:
    return 0;
}

Edited by author 13.01.2011 02:22

print out your answer with end line.

cout << res << endl;

Greedy algorithm is wrong! You should check all 2^n situations.

why the wrong ... it calculates all the results correctly, you can check yourself

You can find some tests on the forum and check yourself that greedy algo is wrong.

I know that the greedy algorithm is not always appropriate, but in this case, it should work