Codeforces 600E. Lomsat gelral

学习了一下dsu on tree

所以为啥是dsu而不是dfs on tree？？？

这道题先把这棵树轻重链剖分了，然后先处理轻儿子，处理完轻儿子后要把轻儿子的贡献都给删了

然后为了计算这个点的贡献，我把所有轻儿子的贡献加回来

如果这个点是个轻儿子，没什么人权，我就再遍历整棵树把它清空

其实我希望的是把整个数组清空，又不能一个一个清，所以把当前子树遍历一遍清空

唔，感觉说的好短，但是确实是这样的……

#include 
    
     #define fi first#define se second#define pii pair
     
      #define mp make_pair#define pb push_back#define space putchar(' ')#define enter putchar('\n')#define eps 1e-10#define MAXN 100005#define ba 47//#define ivorysiusing namespace std;typedef long long int64;typedef unsigned int u32;typedef double db;template
      
       void read(T &res) {    res = 0;T f = 1;char c = getchar();    while(c < '0' || c > '9') {    if(c == '-') f = -1;    c = getchar();    }    while(c >= '0' && c <= '9') {    res = res * 10 +c - '0';    c = getchar();    }    res *= f;}template
       
        void out(T x) {    if(x < 0) {x = -x;putchar('-');}    if(x >= 10) {    out(x / 10);    }    putchar('0' + x % 10);}struct node {    int to,next;}E[MAXN * 2];int head[MAXN],sumE;int N,c[MAXN],siz[MAXN],son[MAXN];int val[MAXN],mval;int64 sum,ans[MAXN];bool vis[MAXN];void add(int u,int v) {    E[++sumE].to = v;    E[sumE].next = head[u];    head[u] = sumE;}void dfs(int u,int fa) {    siz[u] = 1;    for(int i = head[u] ; i ; i = E[i].next) {    int v = E[i].to;    if(v != fa) {        dfs(v,u);        siz[u] += siz[v];        if(siz[v] > siz[son[u]]) son[u] = v;    }    }}void change(int u,int fa,int k) {    val[c[u]] += k;    if(k == -1) vis[u] = 0;    if(val[c[u]] >= mval) {    if(val[c[u]] > mval) {mval = val[c[u]];sum = 0;}    sum += c[u];    }    for(int i = head[u] ; i ; i = E[i].next) {    int v = E[i].to;    if(v != fa && (!vis[v] || k == -1)) {        change(v,u,k);    }    }}void calc(int u,int fa,bool f) {    for(int i = head[u] ; i ; i = E[i].next) {    int v = E[i].to;    if(v != fa && v != son[u]) {        calc(v,u,0);    }    }    if(son[u]) {calc(son[u],u,1);vis[son[u]] = 1;}    change(u,fa,1);    ans[u] = sum;    if(!f) {change(u,fa,-1);sum = 0;mval = 0;}}void Solve() {    read(N);    for(int i = 1 ; i <= N ; ++i) read(c[i]);    int a,b;    for(int i = 1 ; i < N ; ++i) {    read(a);read(b);    add(a,b);add(b,a);    }    dfs(1,0);    calc(1,0,1);    for(int i = 1 ; i <= N ; ++i) {    out(ans[i]);space;    }    enter;}int main() {#ifdef ivorysi    freopen("f1.in","r",stdin);#endif    Solve();}