cf264 div2E题 E. Caisa and Tree（dfs转化为有根树暴力求解）

#include <set>
#include <map>
#include <cmath>
#include <ctime>
#include <queue>
#include <stack>
#include <cctype>
#include <cstdio>
#include <string>
#include <vector>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
typedef unsigned long long ull;
typedef long long ll;
const int inf = 0x3f3f3f3f;
const double eps = 1e-8;
const int maxn = 1e5+10;
int pa[maxn],tree[maxn];
int n,q;
struct
{
    int to,next;
} e[2*maxn];
int head[maxn],tot,cnt;
bool vis[maxn];
int gcd(int x,int y)
{
    return y == 0 ? x : gcd (y,x%y);
}
void init()
{
    memset(head,-1,sizeof(head));
    memset(pa,-1,sizeof(pa));
    memset(vis,0,sizeof(vis));
    tot = 0;
}
void add(int x,int y)
{
    e[tot].to = y;
    e[tot].next = head[x];
    head[x] = tot++;
}
void dfs(int r,int p)
{
    pa[r] = p;
    vis[r] = 1;
    for (int i = head[r]; ~i; i = e[i].next)
    {
        int v = e[i].to;
        if (!vis[v])
            dfs(v,r);
    }
}
int main(void)
{
    freopen("in.txt","r",stdin);
    freopen("out.txt","w",stdout);
    while (~scanf("%d%d",&n,&q))
    {
        for (int i = 1; i <= n; i++)
        {
            scanf ("%d",tree+i);
        }
        int u,v;
        init();
        for (int i = 0; i < n-1; i++)
        {
            scanf("%d%d",&u,&v);
            add(u,v),add(v,u);
        }
        dfs(1,-1);
        for (int i = 0; i < q; i++)
        {
            int d;
            scanf("%d",&d);
            if (d==2)
            {
                scanf("%d%d",&u,&v);
                tree[u] = v;
            }
            else
            {
                int ans = -1;
                scanf("%d",&u);
                int tmp = u;
                while (pa[u] != -1)
                {
                    u = pa[u];
                    if ( gcd(tree[u],tree[tmp])>1)
                    {
                        ans = u;
                        break;
                    }
                }
                printf("%d\n",ans);
            }
        }
    }
    return 0;
}