題意:
求以爲根的子樹中,出現顏色次數最多的顏色編號之和。
思路:
先考慮最暴力的解法:枚舉每個節點,dfs其子樹暴力求解,複雜度
我們可以先重鏈剖分出每個節點的重兒子,處理輕鏈的答案然後合併到重兒子上,更新答案後消除輕兒子對答案的貢獻,複雜度
#include<iostream>
#include<algorithm>
#include<cstdio>
#include<stdio.h>
#include<string.h>
#include<queue>
#include<cmath>
#include<map>
#include<set>
#include<vector>
using namespace std;
#define inf 0x3f3f3f3f
#define lson l,mid,rt<<1
#define rson mid+1,r,rt<<1|1
#define mem(a,b) memset(a,b,sizeof(a));
#define lowbit(x) x&-x;
#define debugint(name,x) printf("%s: %d\n",name,x);
#define debugstring(name,x) printf("%s: %s\n",name,x);
typedef long long ll;
typedef unsigned long long ull;
const double eps = 1e-6;
const int maxn = 1e5+5;
const ll mod = 1e9+7;
inline int read()
{
int x=0,f=1;char ch=getchar();
while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
return x*f;
}
vector<int>g[maxn];
ll kind[maxn],ans[maxn],n,mx,sum,col[maxn],son[maxn],sz[maxn],wson;
void dfs(int u,int fa){ //重鏈剖分
sz[u] = 1;
for(auto v:g[u]){
if(v == fa) continue;
dfs(v,u);
sz[u] += sz[v];
if(sz[v] > sz[son[u]]){
son[u] = v;
}
}
}
void solve(int u,int fa,int val){
kind[col[u]] += val;
if(kind[col[u]] > mx){
mx = kind[col[u]];
sum = col[u];
}
else if(kind[col[u]] == mx){
sum += col[u];
}
for(auto v:g[u]){
if(v == fa || v == wson) continue;
solve(v,u,val);
}
}
void dfsans(int u,int fa,int opt){ //opt表示是否要消除貢獻
for(auto v:g[u]){
if(v == fa) continue;
//dfsans(v,u,opt);
if(v != son[u]){
dfsans(v,u,0); //處理輕鏈
}
}
if(son[u]){
dfsans(son[u],u,1); //處理重鏈
wson = son[u];
}
solve(u,fa,1); //處理輕鏈的答案
wson = 0;
ans[u] = sum;
if(!opt) solve(u,fa,-1),mx = 0,sum = 0; //消除當前節點輕鏈的貢獻
}
int main(){
scanf("%d",&n);
for(int i = 1; i <= n; i++)
scanf("%lld",&col[i]);
for(int i = 1; i < n; i++){
int u,v;
scanf("%d%d",&u,&v);
g[u].push_back(v);
g[v].push_back(u);
}
dfs(1,0);
dfsans(1,0,0);
for(int i = 1; i <= n; i++)
printf("%lld ",ans[i]);
}