洛谷P1157----组合数的输出

#include<stdio.h>
int a[21] = { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 };
int result[21];
int n, r;
int j = 0;
void dfs(int x) {//x表示当前是第几个数
    int ii;
    if (x > r) {
        for (ii = 0; ii < r; ii++) {
            printf("%3d", result[ii]);
        }
        printf("\n");
        return;
    }
    for (ii = x; ii <=n-r+x; ii++) {
        if (a[ii] == 0&&(x==1||ii>result[x-2])) {//每个数都必须比他的前一个数大
            a[ii] = 1;
            result[x-1] = ii;
            dfs(x + 1);
            a[ii] = 0;
        }
    }
}

int main() {
    
    scanf("%d %d", &n, &r);
    dfs(1);
    return 0;
}