hdu 1258 从n个数中找和为t的组合 (DFS)

题意：首先给你一个t，然后是n，后面输入n个数，然后让你求的是n个数中和为t的序列总共有多少种，把他们按从左到右的顺序输出来。

Sample Input
4 6 4 3 2 2 1 1
5 3 2 1 1
400 12 50 50 50 50 50 50 25 25 25 25 25 25
0 0

Sample Output
Sums of 4:
4
3+1
2+2
2+1+1
Sums of 5:
NONE
Sums of 400:
50+50+50+50+50+50+25+25+25+25
50+50+50+50+50+25+25+25+25+25+25

# include <cstdio>
# include <cmath>
# include <iostream>
# include <cstring>
# include <algorithm>
using namespace std ;

int a[20] ;
int save[20] ;
int  n , t ;
bool flag ;

bool cmp(const int &x , const int &y)
{
    return x > y ;
}

void dfs(int count , int L , int pos)
{
    if (L > t)
        return  ;
    if (L == t)
    {
        for(int j=0;j<count-1;j++)
        {
            printf("%d+",save[j]);
        }
        printf("%d
",save[count-1]);
        flag = 1 ;
        return  ;
    }
    for (int i = pos ; i < n ; i++)
    {
        save[count] = a[i] ;
        dfs (count+1,L+a[i] , i+1) ;
        while (a[i] == a[i+1])
            i++ ;
    }

}

int main()
{
    //freopen("in.txt","r",stdin) ;

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

    return 0 ;

}