Submission #2510305

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Source Code Expand

#include<bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)n;i++)
#define all(c) (c).begin(),(c).end()
#define pb push_back
#define dbg(...) do{cerr<<__LINE__<<": ";dbgprint(#__VA_ARGS__, __VA_ARGS__);}while(0);

using namespace std;

namespace std{template<class S,class T>struct hash<pair<S,T>>{size_t operator()(const pair<S,T>&p)const{return ((size_t)1e9+7)*hash<S>()(p.first)+hash<T>()(p.second);}};template<class T>struct hash<vector<T>>{size_t operator()(const vector<T> &v)const{size_t h=0;for(auto i : v)h=h*((size_t)1e9+7)+hash<T>()(i)+1;return h;}};}
template<class T>ostream& operator<<(ostream &os, const vector<T> &v){os<<"[ ";rep(i,v.size())os<<v[i]<<(i==v.size()-1?" ]":", ");return os;}template<class T>ostream& operator<<(ostream &os,const set<T> &v){os<<"{ "; for(const auto &i:v)os<<i<<", ";return os<<"}";}
template<class T,class U>ostream& operator<<(ostream &os,const map<T,U> &v){os<<"{";for(const auto &i:v)os<<" "<<i.first<<": "<<i.second<<",";return os<<"}";}template<class T,class U>ostream& operator<<(ostream &os,const pair<T,U> &p){return os<<"("<<p.first<<", "<<p.second<<")";}
void dbgprint(const string &fmt){cerr<<endl;}template<class H,class... T>void dbgprint(const string &fmt,const H &h,const T&... r){cerr<<fmt.substr(0,fmt.find(","))<<"= "<<h<<" ";dbgprint(fmt.substr(fmt.find(",")+1),r...);}
typedef long long ll;typedef vector<int> vi;typedef pair<int,int> pi;const int inf = (int)1e9;const double INF = 1e12, EPS = 1e-9;

int dp[100010][2]; //dp[v][下向き]
int n, col[100010], deg[100010], white[100010], cost, ans;
vector<vi> e;

void rec(int c, int p){
	white[c] += col[c];
	vector<pi> a, b;
	
	deg[c] = c != p;
	for(int i : e[c]) if(i != p){
		rec(i, c);
		if(!white[i]) continue;
		deg[c]++;
		white[c] += white[i];
		cost += 2;
	}
	if(!white[c]) return;
	
	for(int i : e[c]) if(i != p && white[i]){
		dp[c][0] = max(dp[c][0], dp[i][0] + (col[c] != deg[c] % 2) - (col[c] != (deg[c] + 1) % 2) + 1);
		dp[c][1] = max(dp[c][1], dp[i][1] + (col[i] != deg[i] % 2) - (col[i] != (deg[i] + 1) % 2) + 1);
		
		a.emplace_back(dp[i][0] + (col[c] != deg[c] % 2) - (col[c] != (deg[c] + 1) % 2) + 1, i);
		b.emplace_back(dp[i][1] + (col[i] != deg[i] % 2) - (col[i] != (deg[i] + 1) % 2) + 1, i);
		
		//if(i == 2) dbg(dp[i][1], (int)(col[i] != deg[i] % 2), col[i] != (deg[i] + 1) % 2);
	}
	if(col[c] != deg[c] % 2) cost++;
	sort(all(a), greater<pi>()); sort(all(b), greater<pi>());
	if(a.size()) ans = max(ans, a[0].first);
	if(b.size()) ans = max(ans, b[0].first);
	
	//dbg(c, a);
	
	rep(i, 2) rep(j, 2) if(i < a.size() && j < b.size() && a[i].second != b[j].second){
		//if(ans < a[i].first + b[j].first) dbg(c, ans, i, j, a[i], b[j])
		ans = max(ans, a[i].first + b[j].first);
	}
}

int main(){
	cin.tie(0); cin.sync_with_stdio(0);
	cin >> n; e.resize(n);
	rep(i, n - 1){
		int a, b; cin >> a >> b; a--; b--;
		e[a].pb(b);
		e[b].pb(a);
	}
	{
		string s; cin >> s;
		rep(i, n) col[i] = s[i] == 'W';
	}
	rep(i, n) if(col[i]){
		rec(i, i);
		break;
	}
	dbg(cost, ans);
	cout << cost - ans << endl;
	
	return 0;
}

Submission Info

Judge Result