最近公共祖先LCA tarjan

/*    最近公共祖先LCA    tarjan    by sbn*/#include<iostream>#include<cstdio>#include<cstring>using namespace std;struct edge{        int x,y,nxt;        edge(){}        edge(int nx,int ny,int nnxt){                x=nx;y=ny;nxt=nnxt;        }}  E[1000001],Q[1000001];int n,m,root,cnte,cntq,lca[1000001];int s,father[500001];bool vis[500001];int heade[500001],headq[500001];inline void link_e(int x,int y){        E[++cnte]=edge(x,y,heade[x]);        E[++cnte]=edge(y,x,heade[y]);        heade[x]=cnte-1;        heade[y]=cnte;}inline void link_q(int x,int y){    Q[++cntq]=edge(x,y,headq[x]);    headq[x]=cntq;    Q[++cntq]=edge(y,x,headq[y]);    headq[y]=cntq;}int getfather(int x){        if (father[x]==x) return x;             father[x]=getfather(father[x]);            return father[x];}void dfs(int x){        vis[x]=1;        int k=heade[x];        while (k!=0){            if (!vis[E[k].y])                {dfs(E[k].y);father[getfather(E[k].y)]=getfather(x);}            k=E[k].nxt;        }        k=headq[x];        while (k!=0){                    if (vis[Q[k].y])                        lca[(k+1)/2]=getfather(Q[k].y);            k=Q[k].nxt;        }}int read(){    int x=0;char ch=getchar();    while(ch<'0'||ch>'9')ch=getchar();    while(ch>='0'&&ch<='9')x=x*10+ch-'0',ch=getchar();    return x;}int main(){    //freopen("tarjan.txt","r",stdin);        n=read();        m=read();        s=read();        for (int i=1;i<=n-1;i++)            {       int a=read(),b=read();                link_e(a,b);        }        //freopen("tarjan.txt","w",stdout);        for (int i=1;i<=n;i++)            father[i]=i;        for (int i=1;i<=m;i++)            {   int a=read(),b=read();                    link_q(a,b);            }        //cout<<cntq<<endl;        dfs(s);        for (int i=1;i<=cntq/2;i++)            printf("%d\n",lca[i]);    return 0;   }