HDU 1455 http://acm.hdu.edu.cn/showproblem.php?pid=1455

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#include<string.h>
#define N 70

int f, vis[N], v, n, a[N];

int cmp(const void *a, const void *b)
{
    return *(int *)b - *(int *)a;
}

void DFS(int w, int sum)
{
    int i;
    if(sum == 0)
        f = 1;
    else
    {
        for(i = 0 ; i < n && f == 0; i++)
        {
            if(!vis[i] && w - a[i] >= 0)
            {
                vis[i] = 1;
                if(w - a[i] == 0)
                    DFS(v, sum - a[i]);
                else
                    DFS(w - a[i], sum - a[i]);
                vis[i] = 0;
                if(w == a[i])
                    return ;
                if(w == v && a[i] < v)
                    return ;
                while(a[i] == a[i + 1])
                    i++;
            }
        }
    }
}
int main()
{
    int i, sum;
    while(scanf("%d", &n), n)
    {
        sum = f = 0;
        for(i = 0 ; i < n ; i++)
        {
            scanf("%d", &a[i]);
            sum += a[i];
        }
        qsort(a, n, sizeof(a[0]), cmp);
        for(v = a[0] ; v <= sum ; v++)
        {
            if(sum % v == 0)
            {
                if(sum == v)
                    printf("%d
", sum);
                else
                {
                    memset(vis, 0, sizeof(vis));
                    DFS(v, sum);
                    if(f == 1)
                    {
                        printf("%d
", v);
                        break;
                    }
                }
            }
        }
    }
    return 0;
}