Rochambeau---poj2912||zoj2751(并查集类似于食物链)

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <stack>
#include <map>
#include <vector>
using namespace std;
typedef long long LL;
#define N 2520
#define met(a, b) memset(a, b, sizeof(a))

int f[N], r[N], wrong[N];

int Find(int x)
{
    int k = f[x];
    if(x!=f[x])
    {
        f[x] = Find(f[x]);
        r[x] = (r[x]+r[k])%3;
    }
    return f[x];
}

struct node
{
    int x, y, op;
}a[N];
int main()
{
    int n, m;
    while(scanf("%d %d", &n, &m)!=EOF)
    {
        met(a, 0);

        for(int i=1; i<=m; i++)
        {
            char ch;
            scanf("%d%c%d", &a[i].x, &ch, &a[i].y);
            if(ch == ‘=‘) a[i].op = 0;
            if(ch == ‘>‘) a[i].op = 1;
            if(ch == ‘<‘) a[i].op = 2;
        }

        for(int i=0; i<n; i++)///枚举裁判；
        {
            for(int j=0; j<n; j++)
                f[j] = j, r[j] = 0;

            wrong[i] = 0;///第i个人当裁判的时候在哪产生矛盾；
            for(int j=1; j<=m; j++)
            {
                if(a[j].x == i || a[j].y == i)continue;
                int x = a[j].x, y = a[j].y;

                int px = Find(x);
                int py = Find(y);

                if(px != py)
                {
                    f[px] = py;
                    r[px] = (r[y] + a[j].op - r[x] + 3)%3;
                }
                else if(px == py && (r[y]+a[j].op)%3 != r[x])
                {
                    wrong[i] = j;
                    break;
                }
            }
        }
        int judge = 0, ans = 0, Index;
        for(int i=0; i<n; i++)
        {
            if(wrong[i] == 0)
            {
                judge++;
                Index = i;
            }
            ans = max(wrong[i], ans);///当其他的情况矛盾了，那么就是确定结果的时候；
        }
        if(judge == 1) printf("Player %d can be determined to be the judge after %d lines\n", Index, ans);
        else if(judge == 0) printf("Impossible\n");///没有产生；
        else printf("Can not determine\n");///产生的不止一个，就是不确定；
    }
    return 0;
}