1118 Birds in Forest

题意：

思路：并查集模板题。

代码：

#include <cstdio>
#include <algorithm>
using namespace std;
const int maxn=10005;
int father[maxn];
int birdSet[maxn]={0};

void Init()
{
    for(int i=1;i<maxn;i++)
        father[i]=i;
}

int FindSet(int a)
{
    int root=a;
    while(father[root]!=root)
        root=father[root];
    //剪枝，(不剪枝会超时哦)
    while(father[a]!=a){
        int tmp=a;
        a=father[a];
        father[tmp]=root;
    }
    return root;
}

void Union(int a,int b)
{
    int seta=FindSet(a);
    int setb=FindSet(b);
    if(seta!=setb) father[setb]=seta;
}

int main()
{
    //freopen("pat.txt","r",stdin);
    Init();
    int n,m,pre,curr;
    int birdCnt=0;
    scanf("%d",&n);
    for(int i=0;i<n;i++){
        scanf("%d%d",&m,&pre);
        if(pre>birdCnt) birdCnt=pre;
        for(int j=1;j<m;j++){
            scanf("%d",&curr);
            if(curr>birdCnt) birdCnt=curr;
            Union(pre,curr);
            pre=curr;
        }
    }
    for(int i=1;i<=birdCnt;i++)
        birdSet[FindSet(i)]++;
    int setCnt=0;
    for(int i=1;i<=birdCnt;i++)
        if(birdSet[i]!=0) setCnt++;
    printf("%d %d\n",setCnt,birdCnt);
    int query,a,b;
    scanf("%d",&query);
    for(int i=0;i<query;i++){
        scanf("%d%d",&a,&b);
        if(FindSet(a)==FindSet(b)) printf("Yes\n");
        else printf("No\n");
    }
    return 0;
}