제출 #676687

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
676687		QwertyPi	Islands (IOI08_islands)	C++14	80 / 100	689 ms	131072 KiB

islands

#include <bits/stdc++.h>
#define fi first
#define se second
using namespace std;

const int N = 1e6 + 11;

// 40
vector<pair<int, int>> G[N];
int p[N], w[N], tin[N], t = 0;
long long dp[N];
bool vis[N], cyc[N];

// 12
struct edge{
	int u, v, w;
};
vector<edge> extra;

void dfs(int id, int v, int pa = -1){
	vis[v] = true; tin[v] = ++t;
	for(auto i : G[v]){
		if(!vis[i.fi]){
			p[i.fi] = v;
			dfs(id, i.fi, v);
			w[i.fi] = i.se;
		}else if(i.fi != pa){
			extra[id] = {v, i.fi, i.se};
		}
	}
}

bool is_anc(int u, int v){
	return tin[u] <= tin[v];
}

long long dfs_dp(int id, int v, int pa = -1){
	// 8
	vector<long long> dis;
	long long ans = 0;
	for(auto i : G[v]){
		if(!cyc[i.fi] && i.fi != pa){
			long long r = dfs_dp(id, i.fi, v);
			ans = max(ans, r);
			dis.push_back(dp[i.fi] + i.se);
		}
	}
	sort(dis.begin(), dis.end());
	if(dis.size() >= 2) ans = max(ans, dis.back() + dis[dis.size() - 2]);
	if(dis.size()) dp[v] = dis.back(), ans = max(ans, dis.back());
	return ans;
}

// 32
struct SegTree{
	long long t[1 << 22];
	void upd(int pos, long long val, int v, int l, int r){
		if(l == r) return void(t[v] = val);
		int m = (l + r) / 2;
		if(pos <= m){
			upd(pos, val, v * 2 + 1, l, m);
		}else{
			upd(pos, val, v * 2 + 2, m + 1, r);
		}
		t[v] = max(t[v * 2 + 1], t[v * 2 + 2]);
	}
	long long qry(int ql, int qr, int v, int l, int r){
		if(qr < l || r < ql) return 0;
		if(ql <= l && r <= qr) return t[v];
		int m = (l + r) / 2;
		long long qa = qry(ql, qr, v * 2 + 1, l, m);
		long long qb = qry(ql, qr, v * 2 + 2, m + 1, r);
		return max(qa, qb);
	}
} segTree;

long long solve(int id, vector<long long>& DP, vector<int>& W){
	int n = W.size();
	// 16
	vector<long long> S(n * 2 + 1);
	S[0] = 0;
	for(int i = 0; i < n; i++){
		S[i + 1] = S[i] + W[i];
	}
	for(int i = 0; i < n; i++){
		S[n + i + 1] = S[n + i] + W[i];
	}
	
	for(int i = 0; i < n * 2; i++){
		segTree.upd(i, S[i] + DP[i % n], 0, 0, n * 2 - 1);
	}
	long long ans = 0;
	for(int i = 0; i < n; i++){
		ans = max(ans, DP[i] - S[i] + segTree.qry(i + 1, i + n - 1, 0, 0, n * 2 - 1));
	}
	return ans;
}

int32_t main(){
	cin.tie(0); cout.tie(0)->sync_with_stdio(false);
	int n; cin >> n;
	for(int i = 1; i <= n; i++){
		int v, _w; cin >> v >> _w;
		G[i].push_back({v, _w});
		G[v].push_back({i, _w});
	}
	for(int i = 1; i <= n; i++){
		G[i].shrink_to_fit();
	}
	
	// 4
	vector<int> roots;
	for(int i = 1; i <= n; i++){
		if(!vis[i]){
			extra.resize(extra.size() + 1);
			dfs(roots.size(), i);
			roots.push_back(i);
		}
	}
	
	// 20
	int CC = roots.size();
	long long ans = 0;
	for(int i = 0; i < CC; i++){
		vector<int> cyc_L, cyc_R;
		int x = extra[i].u, y = extra[i].v;
		while(!is_anc(x, y)){
			cyc[x] = true;
			cyc_L.push_back(x);
			x = p[x];
		}
		while(!is_anc(y, x)){
			cyc[y] = true;
			cyc_R.push_back(y);
			y = p[y];
		}
		int l = x;
		cyc[l] = true;
		long long rans = 0;
		for(auto v : cyc_L){
			rans = max(rans, dfs_dp(i, v));
		}
		for(auto v : cyc_R){
			rans = max(rans, dfs_dp(i, v));
		}
		rans = max(rans, dfs_dp(i, l));
		vector<int> W; vector<long long> DP;
		for(auto i : cyc_L){
			DP.push_back(dp[i]);
			W.push_back(w[i]);
		}
		DP.push_back(dp[l]);
		for(int i = (int) cyc_R.size() - 1; i >= 0; i--){
			DP.push_back(dp[cyc_R[i]]);
			W.push_back(w[cyc_R[i]]); 
		}
		cyc_L.resize(0); cyc_R.resize(0);
		W.push_back(extra[i].w);
		rans = max(rans, solve(i, DP, W));
		ans += rans;
	}
	cout << ans << endl;
}

• Subtask 1: 33 / 33
• Subtask 2: 3 / 3
• Subtask 3: 4 / 4
• Subtask 4: 10 / 10
• Subtask 5: 10 / 10
• Subtask 6: 10 / 10
• Subtask 7: 10 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10