记录编号	355097	评测结果	AAAAAAAAAA
题目名称	奶牛议会	最终得分	100
用户昵称	sxysxy	是否通过	通过
代码语言	C++	运行时间	0.048 s
提交时间	2016-11-23 19:51:17	内存使用	0.40 MiB

#include <cstdio>
#include <cstring>
#include <cstdarg>
#include <cstdlib>
#include <cctype>
#include <vector>
using namespace std;
#define MAXN 4040
bool mark[MAXN];
int rec[MAXN];
int rec_top;
int n;
vector<int> G[MAXN];
void add_assert(int x, int xv, int y, int yv)
{
    x = (x<<1)|xv;
    y = (y<<1)|yv;
    G[x^1].push_back(y);
    G[y^1].push_back(x);
}
bool dfs(int x)
{
    if(mark[x^1])return false;
    if(mark[x])return true;
    mark[x] = true;
    rec[rec_top++] = x;
    for(int i = 0; i < G[x].size(); i++)
        if(!dfs(G[x][i]))return false;
    return true;
}
inline int fast_read()
{
    int r;
    char c;
    bool sig = false;
    while(c = getchar())
    {
        if(c >= '0' && c <= '9')
        {
            r = c^0x30;
            break;
        }else if(c == '-')sig = true;
    }
    while(isdigit(c = getchar()))
        r = (r<<3)+(r<<1)+(c^0x30);
    return sig?-r:r;
}
int p1[MAXN];
int p2[MAXN];
int main()
{
    freopen("cowngress.in", "r", stdin);
    freopen("cowngress.out", "w", stdout);
    int n, m;
    n = fast_read();
    m = fast_read();
    for(int i = 0; i < m; i++)
    {
        char c;
        int x = fast_read();
        while(!isalpha(c = getchar()));
        int xv = c=='Y';
        int y = fast_read();
        while(!isalpha(c = getchar()));
        int yv = c=='Y';
        add_assert(x, xv, y, yv);
    }
    for(int i = 1; i <= n; i++)
    {
        int k = i<<1;
        rec_top = 0;
        p1[i] = dfs(k);
        while(rec_top)mark[rec[--rec_top]] = false;
        rec_top = 0;
        p2[i] = dfs(k^1);
        while(rec_top)mark[rec[--rec_top]] = false;
        if(!p1[i] && !p2[i]) //
        {
            puts("IMPOSSIBLE");
            return 0;
        }
    }
    for(int i = 1; i <= n; i++)
    {
        if(p1[i] && !p2[i])putchar('N');
        else if(!p1[i] && p2[i])putchar('Y');
        else if(p1[i] && p2[i])putchar('?');
    }
    return 0;
}