Codeforces 620E New Year Tree（线段树+位运算）

题目链接 New Year Tree

考虑到$ck <= 60$，那么用位运算统计颜色种数

对于每个点，重新标号并算出他对应的进和出的时间，然后区间更新+查询。

用线段树来维护。

 #include <bits/stdc++.h>

 using namespace std;

 #define rep(i, a, b) for (int i(a); i <= (b); ++i)

 struct node{
     long long num, lazy;
 } tree[ << ];

 struct Node{
     int l, r;
 } e[];

 vector <int> v[];

 int n, m;
 long long val[], c[];
 int Time;
 bool vis[];
 long long ans, cover;
 int op;
 int x, y;

 void dfs(int x, int fa){
     e[x].l = ++Time;
     val[Time] = c[x];
     vis[x] = true;
     for (auto u : v[x]){
         if (u == fa) continue;
         dfs(u, x);
     }

     e[x].r = Time;
 }

 inline void pushup(int i){
     tree[i].num = tree[i << ].num | tree[i <<  | ].num;
 }

 inline void pushdown(int i){
     if (tree[i].lazy){
         tree[i << ].num = tree[i <<  | ].num = (1LL << tree[i].lazy);
         tree[i << ].lazy = tree[i <<  | ].lazy = tree[i].lazy;
         tree[i].lazy = ;
     }
 }

 void build(int i, int l, int r){
     tree[i].lazy = ;
     if (l == r){
         tree[i].num = (1LL << val[l]);
         return ;
     }

     int mid = (l + r) >> ;
     build(i << , l, mid);
     build(i <<  | , mid + , r);
     pushup(i);
 }

 void update(int i, int L, int R, int l, int r, long long cover){
     if (l <= L && R <= r){
         tree[i].lazy = cover;
         tree[i].num = (1LL << cover);
         return ;
     }

     int mid = (L + R) >> ;
     pushdown(i);
     if (l <= mid) update(i << , L, mid, l, r, cover);
     if (r > mid) update(i <<  | , mid + , R, l, r, cover);
     pushup(i);
 }

 void solve(int i, int L, int R, int l, int r){
     if (l <= L && R <= r){
         ans |= tree[i].num;
         return;
     }

     pushdown(i);
     int mid = (L + R) >> ;
     if (l <= mid) solve(i << , L, mid, l, r);
     if (r > mid) solve(i <<  | , mid + , R, l, r);
 }

 int main(){

     scanf("%d%d", &n, &m);

     rep(i, , n) v[i].clear();
     rep(i, , n) scanf("%lld", c + i);
     rep(i, , n - ){
         scanf("%d%d", &x, &y);
         v[x].push_back(y);
         v[y].push_back(x);
     }

     memset(vis, , sizeof vis); Time = ;
     dfs(, );
     build(, , n);

     rep(i, , m){
         scanf("%d%d", &op, &x);
         if (op == ){
             scanf("%lld", &cover);
             update(, , n, e[x].l, e[x].r, cover);
         }

         else{
             ans = ;
             solve(, , n, e[x].l, e[x].r);
             int ret = ;
             for (; ans; ans -= ans & -ans) ++ret;
             printf("%d\n", ret);
         }
     }

     return ;
 }