cf 990G - GCD Counting

题意

#include<bits/stdc++.h>
#define t 200000
#define MAXN 200100
using namespace std;

int n;
int fa[MAXN],fa1[MAXN];
long long ans[MAXN],size[MAXN];
vector <int> e[MAXN],Edge[MAXN];

int find(int x){
    if (x==fa1[x])
        return fa1[x];
    else
        return fa1[x]=find(fa1[x]);
}

void dfs(int x,int y){
    int x1,x2;
    x1=Edge[x].size();
    for (int i=0;i<x1;i++){
        x2=Edge[x][i];
        if(x2==y)
            continue;
        fa[x2]=x;
        dfs(x2,x);
    }
}

int main(){
    scanf("%d",&n);
    int x,y;
    for (int i=1;i<=n;i++){
        scanf("%d",&x);
        e[x].push_back(i);
    }
    for (int i=1;i<=n-1;i++){
        scanf("%d %d",&x,&y);
        Edge[x].push_back(y);
        Edge[y].push_back(x);
    }
    dfs(1,-1);
    for (int i=1;i<=t;i++){
        for (int j=i;j<=t;j+=i){
            ans[i]+=e[j].size();
            x=e[j].size();
            for (int k=0;k<x;k++){
                int y=e[j][k];
                fa1[y]=y;
                size[y]=1;
            }
        }

        for (int j=i;j<=t;j+=i){
            x=e[j].size();
            for (int k=0;k<x;k++){
                int y=e[j][k];
                if (y==1)
                    continue;
                if (fa1[fa[y]]==0)
                    continue;
                int x1=find(y);
                int y1=find(fa[y]);
                ans[i]=ans[i]+size[x1]*size[y1];
                fa1[x1]=y1;
                size[y1]+=size[x1];
            }
        }

        for (int j=i;j<=t;j+=i){
            x=e[j].size();
            for (int k=0;k<x;k++){
                int y=e[j][k];
                fa1[y]=0;
                size[y]=0;
            }
        }
    }

    for (int i=t;i>=1;i--)
        for (int j=i*2;j<=t;j+=i)
            ans[i]-=ans[j];

    for (int i=1;i<=t;i++)
        if (ans[i])
            printf("%d %lld\n",i,ans[i]);
    return 0;
}