power-set.c

#include <stdio.h>
#include <string.h>

void print_result(int result[], int len) {
	int i;
	if(len == 0)
		printf("NOTHING\n");
	else {
		for(i = 0; i < len; i++)
			printf("%d ", result[i]);
		printf("\n");
	}
}

void power_set(int choice, int pos, int remain, int result[]) {
	if(remain == 0) {
		print_result(result, pos);
		return ;
	}

	result[pos] = choice;
	power_set(choice+1, pos+1, remain-1, result);
	power_set(choice+1, pos, remain-1, result);
}

int main(void) {
	int N;
	int result[10];
	scanf("%d", &N);
	power_set(1, 0, N, result);
	return 0;
}