zerosum.cpp

USACO chapter two.Useful for beginners.

/*
ID: chenkai4
PROG: zerosum
LANG: C++
*/
#include <iostream>
using namespace std;

int N;

int fuck[10]={0};


void check()
{
	int last=0,now=1;int lasts=2;
	for(int a=2;a<=N;a++)
	{
		if(fuck[a-1]==1)
		{
			now*=10;
			now+=a;
		}
		if(fuck[a-1]==2||fuck[a-1]==3)
		{
			if(lasts==2)
				last+=now;
			else
				last-=now;
			now=a;
			lasts=fuck[a-1];
		}
	}
	if(lasts==2)
		last+=now;
	else
		last-=now;

	if(last==0)
	{
		for(int a=1;a<=N-1;a++)
		{
			printf("%d",a);
			if(fuck[a]==1)
				printf(" ");
			else if(fuck[a]==2)
				printf("+");
			else
				printf("-");
		}
		printf("%d\n",N);
	}
}


void searchit(int n)
{
	if(n==N)
		check();
	else if(n<=N-1)
	{
		fuck[n]=1;
		searchit(n+1);
		fuck[n]=2;
		searchit(n+1);
		fuck[n]=3;
		searchit(n+1);
	}
}

int main()
{

	freopen("zerosum.in","r",stdin);
	freopen("zerosum.out","w",stdout);
	scanf("%d",&N);
	searchit(1);
	return 0;
}