#include <stdio.h>
#include <string.h>
bool grid[26][26];
int color[26];
int lowbit(int x)
{
	return x&(-x);
}
int getColorNum(int x)
{
	switch(x)
	{
		case 0x1:return 1;
		case 0x2:return 2;
		case 0x4:return 3;
		case 0x8:return 4;
	}
}
int main()
{
	char c;
	int n,ans,tmp;
	while(scanf("%d\n",&n)&&n)
	{
		ans=0;
		memset(grid,false,sizeof(grid));
		for(int i=0;i<n;++i)
		{
			getchar();
			getchar();
			while((c=getchar())!='\n')
				grid[i][c-'A']=true;
			color[i]=0xf;
		}
		for(int i=0;i<n;++i)
		{
			color[i]=lowbit(color[i]);
			tmp=getColorNum(color[i]);
			if(tmp>ans)
				ans=tmp;
			if(ans==4)
				break;
			for(int j=i+1;j<n;++j)
				if(grid[i][j])
					color[j]^=color[i];
		}
		ans==1?printf("%d channel needed.\n",ans):printf("%d channels needed.\n",ans);
	}
	return 0;
}

• Re:0ms一发AC，不需要任何搜索，贴一发代码，四色定理直接染 (944) 201824100818 2019-11-18 22:11:52