百练 4004 数字组合

题目链接：http://bailian.openjudge.cn/practice/4004

# include <stdio.h># include <string.h># include <stdlib.h>int NUM = 0;int SUM = 0;int a[100];int t;void sum(int *a,int m,int n){if(m <= 0 || n <= 0)return;int i;for(i = n - 1;i >= 0;i--){SUM += a[i];if(SUM == t)NUM++;else if(m > 1){sum(a,m-1,i);} SUM -= a[i];}}void main(){int i,n;scanf("%d %d",&n,&t);NUM = 0;for(i = 0;i < n;i++)scanf("%d",&a[i]);sum(a,n,n);printf("%d\n",NUM);}