1. 程式人生 > >CF 題目集錦 PART 7 #264 div 2 E

CF 題目集錦 PART 7 #264 div 2 E

【原題】

E. Caisa and Tree time limit per test 10 seconds memory limit per test 256 megabytes input standard input output standard output

Caisa is now at home and his son has a simple task for him.

Given a rooted tree with n vertices, numbered from 1 to n (vertex 1 is the root). Each vertex of the tree has a value. You should answer q

 queries. Each query is one of the following:

  • Format of the query is "1 v". Let's write out the sequence of vertices along the path from the root to vertex vu1, u2, ..., uk (u1 = 1; uk = v). You need to output such a vertex ui that gcd(value of ui, value of v) > 1 and i < k. If there are several possible vertices u
    i
     pick the one with maximum value of i. If there is no such vertex output -1.
  • Format of the query is "2 v w". You must change the value of vertex v to w.

You are given all the queries, help Caisa to solve the problem.

Input

The first line contains two space-separated integers nq (1 ≤ n, q ≤ 105

).

The second line contains n integers a1, a2, ..., an (1 ≤ ai ≤ 2·106), where ai represent the value of node i.

Each of the next n - 1 lines contains two integers xi and yi (1 ≤ xi, yi ≤ nxi ≠ yi), denoting the edge of the tree between vertices xi and yi.

Each of the next q lines contains a query in the format that is given above. For each query the following inequalities hold: 1 ≤ v ≤ n and 1 ≤ w ≤ 2·106Note that: there are no more than 50 queries that changes the value of a vertex.

Output

For each query of the first type output the result of the query.

Sample test(s) input
4 6
10 8 4 3
1 2
2 3
3 4
1 1
1 2
1 3
1 4
2 1 9
1 4
output
-1
1
2
-1
1
Note

gcd(x, y) is greatest common divisor of two integers x and y.


【分析】這道題是做現場賽的。本來能A的,但是太緊張了=而且也不會用vector,邊表搞的麻煩死了。

開始看到修改操作才50次、時間又鬆,真是爽!估計每次可以暴力重構這顆樹,然後對於每個質因子記錄最優值。

首先每次不能sqrt的效率列舉一個數的因子,我們可以預處理出每個數的所有質因子。(其實有更省空間的)

剩下來要解決的問題是:因為我是用dfs的,怎麼把某個子樹的資訊在搜完後再去掉?(以免影響其他子樹)HHD表示用vector一點也不虛。其實應該也可以用邊表類似的思路,但是麻煩= =

【程式碼】

#include<cstdio>
#include<algorithm>
#include<cstring>
#include<vector>
#define N 100005
#define S 2000005
#define push push_back
#define pop pop_back
using namespace std;
vector<int>fac[S],f[S];
int data[N],ans[N],end[N],pf[S],deep[N];
int C,cnt,n,Q,i,x,y,opt;
struct arr{int go,next;}a[N*2];
inline void add(int u,int v){a[++cnt].go=v;a[cnt].next=end[u];end[u]=cnt;}
inline void init()
{
  int H=2000000;
  for (int i=2;i<=H;i++)
    if (!pf[i])
    {
      for (int j=i;j<=H;j+=i)
        fac[j].push(i),pf[j]=1;
    }
}
void dfs(int k,int fa)
{
  int P=data[k];
  for (int i=0;i<fac[P].size();i++)
  {
    int go=fac[P][i],temp=f[go].size();
    if (temp&&deep[f[go][temp-1]]>deep[ans[k]]) ans[k]=f[go][temp-1];
    f[go].push(k);
  }
  for (int i=end[k];i;i=a[i].next)
    if (a[i].go!=fa)
      dfs(a[i].go,k);
  for (int i=0;i<fac[P].size();i++)
    f[fac[P][i]].pop();
}
inline void get_deep(int k,int fa)
{
  for (int i=end[k];i;i=a[i].next)
    if (a[i].go!=fa) deep[a[i].go]=deep[k]+1,get_deep(a[i].go,k);
}
int main()
{
  scanf("%d%d",&n,&Q);
  for (i=1;i<=n;i++)
    scanf("%d",&data[i]);
  for (i=1;i<n;i++)
    scanf("%d%d",&x,&y),add(x,y),add(y,x);
  init();deep[0]=-1;get_deep(1,0);
  memset(ans,0,sizeof(ans));dfs(1,0);
  while (Q--)
  {
    scanf("%d%d",&opt,&x);
    if (opt==1) {printf("%d\n",ans[x]?ans[x]:-1);continue;}
    memset(ans,0,sizeof(ans));
    scanf("%d",&y);data[x]=y;dfs(1,0);
  }
  return 0;
}