bzoj 1787: [Ahoi2008]Meet 紧急集合

Posted 2020-09-16

1787: [Ahoi2008]Meet 紧急集合

Time Limit: 20 Sec  Memory Limit: 162 MB
Submit: 3016  Solved: 1344
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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

 

lca

屠龙宝刀点击就送

#include <ctype.h>
#include <cstring>
#include <cstdio>
#define N 500005

void read (int &x)
{
    x=0;
    char ch=getchar();
    while (!isdigit(ch)) ch=getchar();
    while (isdigit(ch)) x=x*10+ch-‘0‘,ch=getchar();
}
struct node
{
    int next,to;
}edge[N<<1];
int dep[N],head[N<<1],cnt,n,m,dad[N][25];
void add(int u,int v)
{
    cnt++;
    edge[cnt].next=head[u];
    edge[cnt].to=v;
    head[u]=cnt;
}
void dfs(int x)
{
    dep[x]=dep[dad[x][0]]+1;
    for(int i=0;dad[x][i];i++)
    dad[x][i+1]=dad[dad[x][i]][i];
    for(int i=head[x];i;i=edge[i].next)
    {
        if(dad[x][0]!=edge[i].to)
        {
            dad[edge[i].to][0]=x;
            dfs(edge[i].to);
        }
    }
}
void swap(int &x,int &y)
{
    int tmp=x;
    x=y;
    y=tmp;
} 
int lca(int x,int y)
{
    if(dep[x]>dep[y]) swap(x,y);
    for(int i=20;i>=0;i--)
    if(dep[dad[y][i]]>=dep[x]) y=dad[y][i];
    if(x==y) return x;
    for(int i=20;i>=0;i--) 
    if(dad[x][i]!=dad[y][i]) x=dad[x][i],y=dad[y][i];
    return dad[x][0];
}
int main()
{
    read(n);read(m);
    for(int x,y,i=1;i<n;i++)
    {
        scanf("%d%d",&x,&y);
        add(x,y);
        add(y,x);
    }
    dfs(1);
    for(int x,y,z,i=1;i<=m;i++)
    {
        read(x);read(y);read(z);
        int root=lca(x,y)^(lca(x,z))^(lca(y,z));
        int ans=dep[x]+dep[root]-2*dep[lca(x,root)];
        ans+=dep[y]+dep[root]-2*dep[lca(y,root)];
        ans+=dep[z]+dep[root]-2*dep[lca(z,root)];
        printf("%d %d\n",root,ans); 
    }
    return 0;
}