Submission #2501861

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Source Code Expand

#include<deque>
#include<queue>
#include<vector>
#include<algorithm>
#include<iostream>
#include<set>
#include<cmath>
#include<tuple>
#include<string>
#include<chrono>
#include<functional>
#include<iterator>
#include<random>
#include<unordered_set>
#include<array>
#include<map>
#include<iomanip>
#include<assert.h>
using namespace std;
typedef long long int llint;
typedef long double lldo;
#define mp make_pair
#define mt make_tuple
#define pub push_back
#define puf push_front
#define pob pop_back
#define pof pop_front
#define fir first
#define sec second
#define res resize
#define ins insert
#define era erase
//cout<<setprecision(20)
//cin.tie(0);
//ios::sync_with_stdio(false);
const llint mod=1000000007;
const llint big=4.19e18+1;
const long double pai=3.141592653589793238462643383279502884197;
const long double eps=1e-15;
template <class T,class U>void mineq(T& a,U b){if(a>b){a=b;}}
template <class T,class U>void maxeq(T& a,U b){if(a<b){a=b;}}
llint gcd(llint a,llint b){if(a%b==0){return b;}else return gcd(b,a%b);}
llint lcm(llint a,llint b){return a/gcd(a,b)*b;}
template<class T> void SO(T& ve){sort(ve.begin(),ve.end());}
template<class T> void REV(T& ve){reverse(ve.begin(),ve.end());}
int LBI(vector<int>&ar,int in){return lower_bound(ar.begin(),ar.end(),in)-ar.begin();}
int UBI(vector<int>&ar,int in){return upper_bound(ar.begin(),ar.end(),in)-ar.begin();}
vector<vector<int>>go;
vector<bool>need;
string str;
int hru=0;
int solve(int ter,int per){
	//あるパスを選んで、その頂点のパリティによって減らす
	//白なら-2ということ
	if(!need[ter]){return 0;}
	int ha=0,hb=0;
	for(auto it:go[ter]){
		if(it==per){continue;}
		maxeq(hb,solve(it,ter));
		if(ha<hb){swap(ha,hb);}
	}
	if(str[ter]=='W'){ha+=2;}
	maxeq(hru,ha+hb);
	return ha;
}
int main(void){
	int n,i;cin>>n;
	go.res(n);need.res(n);
	for(i=1;i<n;i++){
		int x,y;cin>>x>>y;x--;y--;
		go[x].pub(y);
		go[y].pub(x);
	}
	for(i=0;i<n;i++){need[i]=true;}
	vector<int>ed(n);
	queue<int>que;
	for(i=0;i<n;i++){
		ed[i]=go[i].size();
		if(ed[i]<=1){que.push(i);}
	}
	//cerr<<"de"<<__LINE__<<endl;
	cin>>str;
	while(que.size()>0){
		int ter=que.front();que.pop();
		if(str[ter]=='W'){continue;}
		else{
			need[ter]=false;
			for(auto it:go[ter]){
				if(need[it]){
					ed[it]--;
					if(ed[it]==1){que.push(it);}
				}
			}
		}
	}
	int ans=0,ninu=0;
	for(i=0;i<n;i++){
		if(need[i]){
			ninu++;
			ans+=2;
			int ki=0;
			for(auto it:go[i]){
				if(need[it]){ki++;}
			}
			if(str[i]=='B'){ki++;}
			
			if(ki%2==0){ans++;str[i]='W';}
			else{str[i]='B';}
		}
	}
	if(ninu==1){ans+=2;}
	//cerr<<str<<endl;
	for(i=0;i<n;i++){if(need[i]){solve(i,-1);cout<<ans-hru-2<<endl;return 0;}}
	cout<<0<<endl;
	return 0;
}

Submission Info

Judge Result