poj 3740 Easy Finding dfs

按行搜，当到第i行时，判断对它选还是不选

下面两种dfs是一样的

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

int n,m,vis[305],ar[20][305];

int match()
{
	int i;
	for (i=0;i<m;i++)
	{
		if(vis[i]!=1)return 0;
	}
	return 1;
}

int judge()
{
	int i;
	for (i=0;i<m;i++)
	{
		if(vis[i]>1)return 0;
	}
	return 1;
}

int dfs(int i)
{
	int j,k;
	if (match())return 1;
	for (k=i;k<n;k++)
	{
		for (j=0;j<m;j++)
		{
			vis[j]+=ar[k][j];
		}
		if(judge())if(dfs(k+1))return 1;
		//郁闷啊，太不细心了，这个地方的k一直写成i了，无限TLE
		for (j=0;j<m;j++)
		{
			vis[j]-=ar[k][j];
		}
	}
	return 0;
}

int main()
{
	int i,j;
	while (scanf("%d%d",&n,&m)!=EOF)
	{
		for (i=0;i<n;i++)
			for (j=0;j<m;j++)
				scanf("%d",&ar[i][j]);
		memset(vis,0,sizeof(vis));
		if(dfs(0))printf("Yes, I found it\n");
		else printf("It is impossible\n");
	}
	return 0;
}

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

int n,m,vis[305],ar[20][305];

int match()
{
	int i;
	for (i=0;i<m;i++)
	{
		if(vis[i]!=1)return 0;
	}
	return 1;
}

int judge()
{
	int i;
	for (i=0;i<m;i++)
	{
		if(vis[i]>1)return 0;
	}
	return 1;
}

int dfs(int i)
{
	int j;
	if (match())return 1;
	if(i<n)
	{
		for (j=0;j<m;j++)
		{
			vis[j]+=ar[i][j];
		}
		if(judge())if(dfs(i+1))return 1;
		for (j=0;j<m;j++)
		{
			vis[j]-=ar[i][j];
		}
		if(dfs(i+1))return 1;
	}
	return 0;
}

int main()
{
	int i,j;
	while (scanf("%d%d",&n,&m)!=EOF)
	{
		for (i=0;i<n;i++)
			for (j=0;j<m;j++)
				scanf("%d",&ar[i][j]);
		memset(vis,0,sizeof(vis));
		if(dfs(0))printf("Yes, I found it\n");
		else printf("It is impossible\n");
	}
	return 0;
}