[Ahoi2008]Meet 紧急集合

Posted 2020-10-26 kcfzyhq

1787: [Ahoi2008]Meet 紧急集合

Time Limit: 20 Sec  Memory Limit: 162 MB
Submit: 3892  Solved: 1771
[Submit][Status][Discuss]

Description

Input

Output

Sample Input

6 4
1 2
2 3
2 4
4 5
5 6
4 5 6
6 3 1
2 4 4
6 6 6

Sample Output

5 2
2 5
4 1
6 0

HINT

Source

Day1

 

 

【代码】

#include<cstdio>
#include<cstring>
#include<cmath>
#include<cstdlib>
#include<algorithm>
using std::swap;
const int maxn=500010,maxm=500010;
int ver[maxm<<1],nxt[maxm<<1],head[maxn],en,d[maxn],f[maxn][20],len;

inline void AddEdge(int from,int to) {
    ver[++en]=to,nxt[en]=head[from],head[from]=en;
}
void dfs(int x,int fa) {
    d[x]=d[fa]+1;
    for(int i=head[x]; i; i=nxt[i]) {
        int y=ver[i];
        if(d[y])continue;
        f[y][0]=x;
        for(int j=1; j<=len; j++)f[y][j]=f[f[y][j-1]][j-1];
        dfs(y,x);
    }
}
int LCA(int x,int y) {
    if(d[x]>d[y])swap(x,y);
    for(int i=len; i>=0; i--)
        if(d[f[y][i]]>=d[x])y=f[y][i];
    if(x==y)return x;
    for(int i=len; i>=0; i--)
        if(f[y][i]!=f[x][i])y=f[y][i],x=f[x][i];
    return f[x][0];
}
inline int cal(int a,int b){
    int t=LCA(a,b);
    return d[a]+d[b]-2*d[t]; 
}
int main() {
    en=0;
    memset(head,0,sizeof(head));
    memset(d,0,sizeof(d));
    int n,m,x,y,z;
    scanf("%d%d",&n,&m);
    len=(int)(log(n)/log(2))+1;
    for(int i=1; i<n; i++) {
        scanf("%d%d",&x,&y);
        AddEdge(x,y);
        AddEdge(y,x);
    }
    dfs(1,0);
    for(int i=1; i<=m; i++) {
        scanf("%d%d%d",&x,&y,&z);
        int a=LCA(x,y),b=LCA(x,z),c=LCA(y,z),g;
        if(a==b)
            g=c;
        else if(a==c)
            g=b;
        else g=a;
        printf("%d %d\\n",g,cal(x,g)+cal(y,g)+cal(z,g));
    }
    return 0;
}