Submission #256200

#	Time	Username	Problem	Language	Result	Execution time	Memory
256200		mode149256	Islands (IOI08_islands)	C++14	90 / 100	1084 ms	131076 KiB

islands

/*input
7
3 8
7 2
4 2
1 4
1 9
3 4
2 3
*/
#include <bits/stdc++.h>
using namespace std;

namespace my_template {
typedef long long ll;
typedef long double ld;
typedef complex<ld> cd;

typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef pair<ld, ld> pd;

typedef vector<int> vi;
typedef vector<vi> vii;
typedef vector<ld> vd;
typedef vector<ll> vl;
typedef vector<vl> vll;
typedef vector<pi> vpi;
typedef vector<vpi> vpii;
typedef vector<pl> vpl;
typedef vector<cd> vcd;
typedef vector<pd> vpd;
typedef vector<bool> vb;
typedef vector<vb> vbb;
typedef std::string str;
typedef std::vector<str> vs;

#define x first
#define y second
#define debug(...) cout<<"["<<#__VA_ARGS__<<": "<<__VA_ARGS__<<"]\n"

const ld PI = 3.14159265358979323846264338327950288419716939937510582097494L;

template<typename T>
pair<T, T> operator+(const pair<T, T> &a, const pair<T, T> &b) { return pair<T, T>(a.x + b.x, a.y + b.y); }
template<typename T>
pair<T, T> operator-(const pair<T, T> &a, const pair<T, T> &b) { return pair<T, T>(a.x - b.x, a.y - b.y); }
template<typename T>
T operator*(const pair<T, T> &a, const pair<T, T> &b) { return (a.x * b.x + a.y * b.y); }
template<typename T>
T operator^(const pair<T, T> &a, const pair<T, T> &b) { return (a.x * b.y - a.y * b.x); }

template<typename T>
void print(vector<T> vec, string name = "") {
	cout << name;
	for (auto u : vec)
		cout << u << ' ';
	cout << '\n';
}
}
using namespace my_template;

const int MOD = 1000000007;
const ll INF = std::numeric_limits<ll>::max();
const int MX = 1000000;

int N;
pi edges[MX];
vpi edgesVisos[MX];
bitset<MX> been;
vi circleV;

ll ats = 0;
ll proc = 0;
ll maxDis = 0;
int kur;

void fill(int x) {
	been[x] = true;

	for (auto u : edgesVisos[x])
		if (!been[u.x])
			fill(u.x);

	auto u = edges[x];
	if (!been[u.x])
		fill(u.x);
}

// -1 ner rato
void find_circle(int x) {
	int prad = x;
	int st = x;

	been[x] = true;

	while (true) {
		auto u = edges[x];
		if (been[u.x]) {

			x = u.x;
			st = u.x;

			circleV.emplace_back(x);
			x = edges[x].x;

			while (x != st) {
				circleV.emplace_back(x);
				x = edges[x].x;
			}
			break;
		}

		x = u.x;
		been[x] = true;
	}

	while (prad != st) {
		been[prad] = false;
		prad = edges[prad].x;
	}
}

void longest(int x, int p, ll dis) {
	if (dis > maxDis) {
		maxDis = dis;
		kur = x;
	}

	for (auto u : edgesVisos[x]) {
		if (u.x == p or been[u.x]) continue;
		longest(u.x, x, dis + u.y);
	}
	auto u = edges[x];
	if (u.x == p or been[u.x]) return;
	longest(u.x, x, dis + u.y);
}

void solve() {
	proc = 0;
	for (auto u : circleV)
		been[u] = true;

	int C = (int)circleV.size();

	vl D(C, 0);

	for (int i = 0; i < C; ++i)
	{
		int x = circleV[i];

		ll did = 0;
		ll did2 = 0;

		D[i] = 0;

		for (auto u : edgesVisos[x]) {
			if (been[u.x]) continue;
			maxDis = 0;
			longest(u.x, x, u.y);
			proc = max(proc, maxDis);

			if (maxDis >= did) {
				did2 = did;
				did = maxDis;
			} else if (maxDis > did2) {
				did2 = maxDis;
			}

			D[i] = max(D[i], maxDis);

			maxDis = 0;
			longest(kur, -1, 0);
			proc = max(proc, maxDis);
		}

		proc = max(proc, did + did2);
	}

	deque<pair<ll, int>> dq;
	ll viso = 0;
	for (int i = 0; i < C; ++i) viso += (ll)edges[circleV[i]].y;

	ll suma = edges[circleV[0]].y;

	{
		for (int i = 1; i < C; ++i)
		{
			// edges[circleV[i]].y += edges[i -.y 1];
			ll newVal = suma + D[i];
			suma += (ll)edges[circleV[i]].y;

			while (dq.size() and dq.back().x <= newVal)
				dq.pop_back();

			dq.push_back({newVal, i});
		}

		suma = 0;
		for (int i = 0; i < C; ++i)
		{
			while (dq.size() and dq.front().y <= i) {
				dq.pop_front();
			}

			proc = max(proc, dq.front().x + D[i] - suma);

			ll newVal = D[i] + viso + suma;
			while (dq.size() and dq.back().x <= newVal)
				dq.pop_back();

			dq.push_back({newVal, i + C});
			suma += (ll)edges[circleV[i]].y;
		}
	}

	for (auto u : circleV)
		been[u] = false;

	ats += proc;
}

int main() {
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	cin >> N;
	for (int i = 0; i < N; ++i)
	{
		int a, w;
		cin >> a >> w; a--;

		edges[i] = {a, w};

		// edgesVisos[i].emplace_back(a, w);
		edgesVisos[a].emplace_back(i, w);
	}

	for (int i = 0; i < N; ++i)
	{
		if (been[i]) continue;

		circleV.clear();

		find_circle(i);

		solve();
		fill(i);
	}

	printf("%lld\n", ats);
}

/* Look for:
* special cases (n=1?)
* overflow (ll vs int?)
* the exact constraints (multiple sets are too slow for n=10^6 :( )
* array bounds
*/

• 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: 10 / 10
• Subtask 9: 0 / 10