记录编号	583637	评测结果	AAAAAAAAAA
题目名称	奶牛议会	最终得分	100
用户昵称	┭┮﹏┭┮	是否通过	通过
代码语言	C++	运行时间	0.108 s
提交时间	2023-10-19 20:48:05	内存使用	0.58 MiB

#include <bits/stdc++.h>
using namespace std;
const int N = 2e3+10,M = 1e4+10;
int n,m;
struct made{
	int ver,nx;
}e[M];
int hd[N],tot,cnt,top,num;
int low[N],dfn[N],st[N],color[N];
bool v[N];
void add(int x,int y){
	tot++;
	e[tot].ver = y,e[tot].nx = hd[x],hd[x] = tot;
}

void tarjan(int x){
	low[x] = dfn[x] = ++cnt;
	st[++top] = x,v[x] = 1;
	for(int i = hd[x];i;i = e[i].nx){
		int y = e[i].ver;
		if(!dfn[y])tarjan(y),low[x] = min(low[x],low[y]);
		else if(v[y])low[x] = min(low[x],dfn[y]);
	}
	if(low[x] == dfn[x]){
		num++;int y = 0;
		do{
			y = st[top--];
			v[y] = 0,color[y] = num;
		}while(x != y);
	}
}

void dfs(int x){
	v[x] = 1;
	for(int i = hd[x];i;i = e[i].nx){
	    int y = e[i].ver;
	    if(!v[y])dfs(y);
    }
}//直接遍历 
bool check(int x){
    memset(v,0,sizeof(v));
    dfs(x);
    for(int i = 1;i <= n;i++)
        if(v[i] && v[i+n])return 0;//判断是否矛盾 
    return 1;
}
int main(){
	freopen("cowngress.in","r",stdin);
	freopen("cowngress.out","w",stdout);
	scanf("%d%d",&n,&m);
	for(int i = 1;i <= m;i++){
		int x,y;char p1[2],p2[2];
		scanf("%d%s%d%s",&x,p1,&y,p2);
		if(p1[0] == 'Y' && p2[0] == 'Y')add(x,y+n),add(y,x+n);
		else if(p1[0] == 'Y' && p2[0] == 'N')add(x,y),add(y+n,x+n);
		else if(p1[0] == 'N' && p2[0] == 'Y')add(x+n,y+n),add(y,x);
		else add(x+n,y),add(y+n,x);
	}
	for(int i = 1;i <= 2*n;i++)
	    if(!color[i])tarjan(i);
	for(int i = 1;i <= n;i++)
		if(color[i] == color[i+n]){
			printf("IMPOSSIBLE\n");
			return 0;
		}// 
	for(int i = 1;i <= n;i++){
		int p1 = check(i),p2 = check(i+n);//从两个点判断是否符合 
		if(p1 && p2)printf("?");//都 
		else if(p1)printf("N");
		else printf("Y");
	}
	printf("\n");
	
    return 0;
	 
}