codeforces 593D(并查集 + LCA)

题意不在描述.

首先我们注意到改变每个点的值时，只会变的更小，每次要除的数为1e18 , 由于log2(1e18)　＜＝　６０　．那么最多只需要除以至多60次大于等于2的数变回变成0，所以我们

只以任意一点为根建立有根树，并且在每次遍历一条链时进行压缩，当该路经值为1，应该被压缩，每次走到多余六十个点直接结束。

#include <bits/stdc++.h>#define fst first#define snd second#define ALL(a) a.begin(), a.end()#define clr(a, x) memset(a, x, sizeof a)#define rep(i,x) for(int i=0;i<(int)x;i++)#define rep1(i,x,y) for(int i=x;i<=(int)y;i++)#define LOGN  22typedef long long ll;using namespace std;const int N = 2e5 + 10000;vector<int> tree[N];int fa[N][LOGN],pa[N] , realpa[N];int depth[N];ll val[N*2] , ided[N];void dfs(int u, int p, int d) {    depth[u] = d;  pa[u] = p; realpa[u] = p;    fa[u][0] = p;    for (int i = 0; i < tree[u].size(); ++i) {        if (tree[u][i] != p)            dfs(tree[u][i], u, d + 1);    }}int LCA(int u, int v) {    if (depth[u] > depth[v]) swap(u, v);    for (int i = 0; i < LOGN; ++i) {        if (((depth[v] - depth[u]) >> i) & 1)            v = fa[v][i];    }    if (u == v) return u;    for (int i = LOGN - 1; i >= 0; --i) {        if (fa[u][i] != fa[v][i]) {            u = fa[u][i];            v = fa[v][i];        }    }    return fa[u][0];}void predo(int n) {    int root = 1;  pa[root] = -1;    dfs(root, -1, 0);    depth[0] = -1;    for (int j = 0; j + 1 < LOGN; ++j) {        for (int i = 1; i <= n; ++i) {            if (fa[i][j] < 0) fa[i][j + 1] = -1;            else fa[i][j + 1] = fa[fa[i][j]][j];        }    }}typedef pair<int,int> pii;map<pii,int> M;ll get_c(int u){ return val[ided[u]]; }int n,m;int find(int u){   if(realpa[pa[u]] == -1 || get_c(pa[u]) > 1) return pa[u];   else return pa[u] = find(pa[u]);}ll cal1(int a,int b,ll c){   int lca = LCA(a,b);   int u = a , v = b; ll now = c;   vector<ll> lt,rt;   while(u != v){       if(depth[u] >= depth[v]){            int fau = find(u);            if(depth[fau] < depth[lca]) fau = lca;            if(get_c(u) > 1) lt.push_back(get_c(u));            u = fau;       }       else {            int fav = find(v);            if(depth[fav] < depth[lca]) fav = lca;            if(get_c(v) > 1) rt.push_back(get_c(v));            v = fav;       }       if(lt.size() + rt.size() > 60) return 0;   }   if(rt.size()) reverse(ALL(rt));   rep(i,rt.size()) lt.push_back(rt[i]);   for(int i=0;i<lt.size();i++){       now/=lt[i];   }   return now;}void read(){   scanf("%d %d",&n,&m);   rep(i,n-1){       int u,v; ll w;       scanf("%d %d %I64d",&u,&v,&w);       M[pii(u,v)] = M[pii(v,u)] = 1 + i;       val[1+i] = w;       tree[u].push_back(v);       tree[v].push_back(u);   }   predo(n);   rep1(i,2,n) ided[i] = M[pii(i,realpa[i])] ;   rep1(i,1,m){      ll cmd , x ,y , z;      scanf("%I64d %I64d %I64d",&cmd,&x,&y);      if(cmd == 1) {          scanf("%I64d",&z);          printf("%I64d\n",cal1(x,y,z));      }      else {         val[x] = y;      }   }}int main(){   read();   return 0;}