POJ2492-A Bug's Life-并查集扩展应用

维护一个relation数组，保留着此元素和根元素之间的性别关系。之后就可以判断gay了。

#include <cstdio>
#include <algorithm>
#include <cstring>

using namespace std;

const int maxn=2010;
int T,n,m;

int fa[maxn],rela[maxn];

int Find(int x)
{
    int t;
    if(fa[x] == x) return x;
    t = fa[x];
    fa[x] = Find(fa[x]);
    rela[x] = (rela[x]+rela[t]+1)%2;
    return fa[x];
}

void Union(int x,int y)
{
    int fx=Find(x),fy=Find(y);
    fa[fx] = fy;
    rela[fx] = (rela[y]-rela[x])%2;
}

int main()
{
    scanf("%d",&T);
    for(int kase=1;kase<=T;kase++)
    {
        scanf("%d%d",&n,&m);
        for(int i=1;i<=n;i++)
        {
            fa[i] = i;
            rela[i] = 1;
        }

        int x,y,sus=0;
        for(int i=0;i<m;i++)
        {
            scanf("%d%d",&x,&y);
            if(Find(x) == Find(y))
            {
                if(rela[x] == rela[y]) sus=1;
            }
            else Union(x,y);
        }
        printf("Scenario #%d:
",kase);

        if(sus)
            printf("Suspicious bugs found!

");
        else
            printf("No suspicious bugs found!

");
    }
}