CF1101D GCD Counting

#include<bits/stdc++.h>
#define reg register int
#define il inline
#define numb (ch^‘0‘)
using namespace std;
typedef long long ll;
il void rd(int &x){
    char ch;x=0;bool fl=false;
    while(!isdigit(ch=getchar()))(ch==‘-‘)&&(fl=true);
    for(x=numb;isdigit(ch=getchar());x=x*10+numb);
    (fl==true)&&(x=-x);
}
namespace Miracle{
const int N=2e5+5;
vector<int>p[N],f[N];
int n;
int ans;
struct node{
    int nxt,to;
}e[2*N];
int hd[N],cnt;
void add(int x,int y){
    e[++cnt].nxt=hd[x];
    e[cnt].to=y;
    hd[x]=cnt;
}
void dfs(int x,int fa){
    for(reg i=hd[x];i;i=e[i].nxt){
        int y=e[i].to;
        if(y==fa) continue;
        dfs(y,x);
        for(reg j=0;j<p[x].size();++j){
        //    cout<<" j "<<p[x][j]<<endl;
            for(reg k=0;k<p[y].size();++k){
            //    cout<<" k "<<p[y][k]<<endl;
                if(p[x][j]==p[y][k]){
                    ans=max(ans,f[x][j]+f[y][k]);
                    f[x][j]=max(f[x][j],f[y][k]+1);
                }
            }
        }
    }
}
void div(int x,int id){
    for(reg i=2;(ll)i*i<=x;++i){
        if(x%i==0){
            p[id].push_back(i);
            f[id].push_back(1);
            while(x%i==0) x/=i;
        }
    }
    if(x>1){
        p[id].push_back(x);
        f[id].push_back(1);
    }
}
int main(){
    rd(n);int x;
    bool flag=false;
    for(reg i=1;i<=n;++i){
        rd(x);
        if(x!=1) flag=true;
        div(x,i);
    }
    if(!flag){
        puts("0");return 0;
    }
    ans=1;
    int y;
    for(reg i=1;i<=n-1;++i){
        rd(x);rd(y);
        add(x,y);add(y,x);
    }
    dfs(1,0);
    printf("%d",ans);
    return 0;
}

}
signed main(){
    Miracle::main();
    return 0;
}

/*
   Author: *Miracle*
   Date: 2019/1/17 19:37:47
*/