hdu 1258 Sum It Up

[code] hljs perl">#include<algorithm>
#include<string.h>
using namespace std;
int flag,t,n,a[20],use[20],ans[20];
bool cmp(int x,int y)
{
    return x>y;
}
void dfs(int sum,int now,int cnt)
{
    int i;
    if(sum==t)
    {
        flag++;
        printf("%d",ans[0]);
        for(i=1; i<cnt; i++)
        {
            printf("+%d",ans[i]);
        }
        printf("\n");
        return ;
    }
        for(i=now; i<n; i++)
        {
            if(use[i]==0)
            {
                if(i!=0&&a[i-1]==a[i]&&use[i-1]==0) continue;
                if(sum+a[i]>t) continue;
                ans[cnt]=a[i];
                use[i]=1;
                dfs(sum+a[i],i+1,cnt+1);
                use[i]=0;
            }
        }
}

int main()
{
    int i;
    while(~scanf("%d%d",&t,&n))
    {
        if(t==0&&n==0) break;
        for(i=0; i<n; i++)
            scanf("%d",&a[i]);
        memset(use,0,sizeof(use));
        sort(a,a+n,cmp);
        flag=0;
        printf("Sums of %d:\n",t);
        dfs(0,0,0);
        if(!flag) printf("NONE\n");
    }
    return 0;
}