Submission #885501

#	Time	Username	Problem	Language	Result	Execution time	Memory
885501		Tob	Islands (IOI08_islands)	C++14	15 / 100	384 ms	131072 KiB

islands

#include <bits/stdc++.h>

#define ll long long
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define pb push_back
#define FIO ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0)

using namespace std;

typedef pair <ll, ll> pii;

const int N = 1e6 + 7;

ll n, ro, sp, res;
ll a[N], b[N], dp[N][2][2];
int bio[N];
vector <pii> adj[N];

void Merge(pii& x, ll y) {
	if (y >= x.F) x = {y, x.F};
	else x = {x.F, max(x.S, y)};
}

void dfs(int x) {
	pii p1 = {0, 0}, p2 = {0, 0};
	for (auto y : adj[x]) {
		if (y.F == ro) continue;
		dfs(y.F);
		Merge(p1, dp[y.F][1][0] + y.S);
		Merge(p2, dp[y.F][1][1] + y.S);
	}
	if (x != sp) {
		if (x != ro) dp[x][0][0] = p1.F + p1.S;
		else dp[x][0][1] = p2.F + p2.S;
		dp[x][1][0] = p1.F;
		dp[x][1][1] = p2.F;
	}
	else {
		ll alt = dp[ro][1][1] + b[ro];
		dp[x][0][0] = max(p1.F + p1.S, alt + p1.F);
		dp[x][1][0] = max(alt, p1.F);
		dp[x][1][1] = p1.F;
	}
	res = max(res, max(dp[x][0][0], dp[x][0][1]));
}

int main () {
	FIO;
	cin >> n;
	
	for (int i = 1; i <= n; i++) {
		cin >> a[i] >> b[i];
		adj[a[i]].pb({i, b[i]});
	}
	
	ll sum = 0;
	for (int i = 1; i <= n; i++) {
		if (bio[i]) continue;
		int x = a[i], y = i;
		bio[i] = i;
		while (!bio[x]) {
			bio[x] = i;
			y = x;
			x = a[x];
		}
		if (bio[x] == i) {
			ro = y;
			sp = x;
			res = 0;
			dfs(ro);
			sum += res;
		}
	}
	
	cout << sum;

	return 0;
}

• Subtask 1: 15 / 33
• Subtask 2: 0 / 3
• Subtask 3: 0 / 4
• Subtask 4: 0 / 10
• Subtask 5: 0 / 10
• Subtask 6: 0 / 10
• Subtask 7: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10