CodeForces-600E Lomsat gelral

传送门：CodeForces-600E

思路分析

启发式合并经典题
步骤为：计算轻儿子的贡献，删除轻儿子的贡献，计算重儿子的贡献，再将轻儿子的贡献合并到重儿子上去

用线段树合并做就很暴力了

树上启发式合并代码

#include <functional>
#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdlib>
#include <iomanip>
#include <vector>
#include <string>
#include <cstdio>
#include <chrono>
#include <random>
#include <queue>
#include <stack>
#include <cmath>
#include <map>
#include <set>
#if __cplusplus >= 201103L
#include <unordered_map>
#include <unordered_set>
#endif
#define ls x<<1
#define rs x<<1|1
#define fi first
#define se second
#define ll long long
#define pb push_back
#define mp make_pair
#define fun function
#define sz(x) x.size()
#define lowbit(x) x&(-x)
#define all(x) x.begin(),x.end()
#define mem(a,b) memset(a,b,sizeof(a))
#define IOS ios_base::sync_with_stdio(0); cin.tie(0);cout.tie(0);

using namespace std;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

const int INF = 0x3f3f3f3f;
const int N=1e5+10;

int n,col[N],ma,flag;
int siz[N],cnt[N],son[N];
vector<int>e[N];
ll ans[N],sum;

void dfs1(int u,int fa) {
    siz[u]=1;
    for(auto v:e[u]) {
        if(v==fa) continue;
        dfs1(v,u);
        siz[u]+=siz[v];
        if(siz[v]>siz[son[u]]) son[u]=v;
    }
}

void calc(int u,int fa,int val) {
    cnt[col[u]]+=val;
    if(cnt[col[u]]>ma) {
        ma=cnt[col[u]];
        sum=col[u];
    } else if(cnt[col[u]]==ma) sum+=col[u];

    for(auto v:e[u]) {
        if(v==fa||v==flag) continue;
        calc(v,u,val);
    }
}

void dfs2(int u,int fa,int keep) {
    for(auto v:e[u]) {
        if(v==fa||v==son[u]) continue;
        dfs2(v,u,0);
    }
    if(son[u]) {
        dfs2(son[u],u,1);
        flag=son[u];
    }
    calc(u,fa,1);
    flag=0;
    ans[u]=sum;
    if(!keep){
        calc(u,fa,-1);
        ma=sum=0;
    }
}


int main() {
    IOS;
#ifdef xiaofan
    freopen("1.in","r",stdin);
    freopen("1.out","w",stdout);
#endif

    int n;
    cin>>n;
    for(int i=1;i<=n;i++) cin>>col[i];
    for(int i=1;i<n;i++){
        int u,v;
        cin>>u>>v;
        e[u].push_back(v);
        e[v].push_back(u);
    }
    dfs1(1,1);
    dfs2(1,1,1);
    for(int i=1;i<=n;i++) cout<<ans[i]<<" ";




    return 0;
}
&nbsp;

线段树合并代码

#include <bits/stdc++.h>
#define fi first
#define se second
#define ll long long
#define pb push_back
#define mp make_pair
#define fun function
#define sz(x) (x).size()
#define lowbit(x) (x)&(-x)
#define all(x) (x).begin(),(x).end()
#define mem(a,b) memset(a,b,sizeof(a))

namespace FastIO {
#define BUF_SIZE 100000
#define OUT_SIZE 100000
    bool IOerror=0;
    inline char nc() {
        static char buf[BUF_SIZE],*p1=buf+BUF_SIZE,*pend=buf+BUF_SIZE;
        if(p1==pend) {
            p1=buf;
            pend=buf+fread(buf,1,BUF_SIZE,stdin);
            if(pend==p1) {
                IOerror=1;
                return -1;
            }
        }
        return *p1++;
    }
    inline bool blank(char ch) {
        return ch==' '||ch=='\n'||ch=='\r'||ch=='\t';
    }
    template<class T> inline bool read(T &x) {
        bool sign=0;
        char ch=nc();
        x=0;
        for(; blank(ch); ch=nc());
        if(IOerror)return false;
        if(ch=='-')sign=1,ch=nc();
        for(; ch>='0'&&ch<='9'; ch=nc())x=x*10+ch-'0';
        if(sign)x=-x;
        return true;
    }
    template<class T,class... U>bool read(T& h,U&... t) {
        return read(h)&&read(t...);
    }
#undef OUT_SIZE
#undef BUF_SIZE
};
using namespace std;
using namespace FastIO;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

const int INF = 0x3f3f3f3f;
const int N = 1e5+10;

struct node {
    int ls,rs;
    ll sum,ma;
} tree[N * 40];

int root[N],cnt,a[N];
ll ans[N];
vector<int>e[N];

void pp(int x) {
    int ls=tree[x].ls;
    int rs=tree[x].rs;
    if(tree[ls].ma==tree[rs].ma) {
        tree[x].sum=tree[ls].sum+tree[rs].sum;
        tree[x].ma=tree[ls].ma;
        return ;
    }
    if(tree[ls].ma>tree[rs].ma) {
        tree[x].sum=tree[ls].sum;
        tree[x].ma=tree[ls].ma;
        return ;
    }
    if(tree[rs].ma>tree[ls].ma) {
        tree[x].sum=tree[rs].sum;
        tree[x].ma=tree[rs].ma;
        return ;
    }
}

void ins(int &x,int l,int r,int pos) {
    if(!x) x=++cnt;
    if(l==r) {
        tree[x].ma++;
        tree[x].sum=l;
        return ;
    }
    int mid=l+r>>1;
    if(pos<=mid) ins(tree[x].ls,l,mid,pos);
    else ins(tree[x].rs,mid+1,r,pos);
    pp(x);
}

int merge(int x,int y,int l,int r) {
    if(!x||!y) return x?x:y;
    if(l==r) {
        tree[x].ma+=tree[y].ma;
        return x;
    }
    int mid=l+r>>1;
    tree[x].ls=merge(tree[x].ls,tree[y].ls,l,mid);
    tree[x].rs=merge(tree[x].rs,tree[y].rs,mid+1,r);
    pp(x);
    return x;
}

void dfs(int u,int fa) {
    for(auto v:e[u]) {
        if(v==fa) continue;
        dfs(v,u);
        root[u]=merge(root[u],root[v],1,N);
    }
    ans[u]=tree[root[u]].sum;
}

int main() {

#ifdef xiaofan
    freopen("1.in","r",stdin);
    freopen("1.out","w",stdout);
#endif

    int n;
    read(n);
    for(int i=1; i<=n; i++) {
        read(a[i]);
        ins(root[i],1,N,a[i]);    
    }
    for(int i=1; i<n; i++) {
        int u,v;
        read(u,v);
        e[u].pb(v);
        e[v].pb(u);
    }
    dfs(1,0);
    for(int i=1; i<=n; i++) cout<<ans[i]<<" ";




    return 0;
}