POJ1470Closest Common Ancestors 最近公共祖先LCA 的 离线算法 Tarjan

该算法的详细解释请戳：

http://www.cnblogs.com/Findxiaoxun/p/3428516.html

 

#include<cstdio>

#include<algorithm>

#include<cstring>

#include<vector>

using namespace std;

const int MAXN=905;

int father[MAXN],ancestor[MAXN];

bool visit[MAXN];

int ans[MAXN];

vector<int> map[MAXN];//save the tree

vector<int> query[MAXN];//save the query

int n,t,root;

bool indegree[MAXN];//the indegree to find the root

int getfather(int v){//path compression

    if(father[v]==v)return v;

    return father[v]=getfather(father[v]);

}

void aunion(int u,int v){//??

    int fv=getfather(v),fu=getfather(u);

    father[fv]=fu;

}

void LCA(int id){

    int len=map[id].size();

    for(int i=0;i<len;i++){

        int son=map[id][i];

        LCA(son);

        aunion(id,son);

    }

    visit[id]=1;

    len=query[id].size();

    for(int i=0;i<len;i++){

        int son=query[id][i];

        if(visit[son])

            ans[father[getfather(son)]]++;

    }



}

void init(){

    int x,y,z;

    for(int i=0;i<=n;i++){

        map[i].clear();

        query[i].clear();

    }

    memset(visit,0,sizeof(visit));

    memset(ans,0,sizeof(ans));

    memset(indegree,0,sizeof(indegree));

    for(int i=0;i<=n;i++)father[i]=i;

    for(int i=0;i<n;i++){

        scanf("%d:(%d)",&x,&y);

        for(int j=0;j<y;j++){

            scanf("%d",&z);

            indegree[z]=1;

            map[x].push_back(z);

        }

    }

    scanf("%d",&t);

    while(t--){//this method of the init is really clever

        while(getchar()!='(');

        scanf("%d%d",&x,&y);

        query[x].push_back(y);

        query[y].push_back(x);

    }

    while(getchar()!=')');

    for(int i=1;i<=n;i++)if(!indegree[i])root=i;//find the root;warning:the 0

}

void output(){

    for(int i=1;i<=n;i++){

        if(ans[i]!=0)

            printf("%d:%d\n",i,ans[i]);

    }



}

int main(){

    while(scanf("%d",&n)!=EOF){

        init();

        LCA(root);

        output();

    }

    return 0;

}