Submission #920281

#	Time	Username	Problem	Language	Result	Execution time	Memory
920281		ting39	Cat Exercise (JOI23_ho_t4)	C++17	100 / 100	491 ms	83348 KiB

Main

#include<bits/stdc++.h>
#define int long long
using namespace std;
vector<vector<int>> g,jump;
vector<int> dep;
struct DSU{
	int n;
	vector<int> to,sz,mx,val;
	DSU(int _n):n(_n){
		to.resize(n);
		sz.resize(n,1);
		val.resize(n);
		mx.resize(n);
		for(int i=0;i<n;i++){
			to[i]=i;
			mx[i]=i;
		}
	}
	int fnd(int p){
		if(to[p]==p) return p;
		to[p]=fnd(to[p]);
		return to[p];
	}
	void conn(int a,int b){
		a=fnd(a);
		b=fnd(b);
		if(a==b) return;
		if(sz[a]>sz[b]) swap(a,b);
		to[a]=b;
		sz[b]+=sz[a];
		mx[b]=max(mx[b],mx[a]);
	}
};
void dfs(int pre,int pos){
	for(int i:g[pos]){
		if(i==pre) continue;
		dep[i]=dep[pos]+1;
		jump[i][0]=pos;
		dfs(pos,i);
	}
}
int lca(int a,int b){
	if(dep[a]<dep[b]) swap(a,b);
	int dif=dep[a]-dep[b],c=0;
	while(dif){
		if(dif&1){
			a=jump[a][c];
		}
		c++;
		dif>>=1;
	}
	if(a==b) return a;
	for(int i=20;i>=0;i--){
		if(jump[a][i]!=jump[b][i]){
			a=jump[a][i];
			b=jump[b][i];
		}
	}
	return jump[a][0];
}
int dis(int a,int b){
	int c=lca(a,b);
	return dep[a]+dep[b]-2*dep[c];
}
signed main(){
	int n;
	cin>>n;
	g.resize(n);
	jump.resize(n,vector<int>(21));
	dep.resize(n);
	vector<vector<int>> gg(n);
	vector<int> v(n);
	for(int &i:v){
		cin>>i;
		i--;
	}
	for(int i=0;i<n-1;i++){
		int a,b;
		cin>>a>>b;
		a--;
		b--;
		a=v[a];
		b=v[b];
		g[a].push_back(b);
		g[b].push_back(a);
		gg[max(a,b)].push_back(min(a,b));
	}
	dfs(0,0);
	for(int j=1;j<21;j++){
		for(int i=0;i<n;i++){
			jump[i][j]=jump[jump[i][j-1]][j-1];
		}
	}
	DSU dsu(n);
	for(int i=0;i<n;i++){
		int tmp=0;
		for(int j:gg[i]){
			int a=dis(i,dsu.mx[dsu.fnd(j)])+dsu.val[dsu.fnd(j)];
			if(a>tmp){
				tmp=a;
			}
			dsu.conn(i,j);
		}
		dsu.val[dsu.fnd(i)]=tmp;
	}
	cout<<dsu.val[dsu.fnd(n-1)]<<endl;
}

• Subtask 1: 7 / 7
• Subtask 2: 7 / 7
• Subtask 3: 7 / 7
• Subtask 4: 10 / 10
• Subtask 5: 20 / 20
• Subtask 6: 23 / 23
• Subtask 7: 26 / 26