Submission #57251

#	Time	Username	Problem	Language	Result	Execution time	Memory
57251		PeppaPig	Islands (IOI08_islands)	C++14	100 / 100	768 ms	119168 KiB

islands

#include <bits/stdc++.h>

#define pll pair<long long, long long>
#define x first
#define y second

using namespace std;

const int N = 1e6 + 5;

int n;
pll par[N], dp[N];
long long dm[N], ans;
int deg[N];

int main() {
	scanf("%d", &n);
	for(int i = 1; i <= n; i++) {
		long long v, w;
		scanf("%lld%lld", &v, &w);
		par[i] = pll(v, w);
		deg[v]++;
	}
	queue<int> Q;
	for(int i = 1; i <= n; i++) if(!deg[i]) Q.emplace(i);
	while(!Q.empty()) {
		int now = Q.front();
		Q.pop();
		dm[now] = max(dm[now], dp[now].x + dp[now].y);
		dm[par[now].x] = max(dm[par[now].x], dm[now]);
		long long dis = dp[now].x + par[now].y;
		if(dis > dp[par[now].x].x) swap(dis, dp[par[now].x].x);
		if(dis > dp[par[now].x].y) swap(dis, dp[par[now].x].y);
		if(!--deg[par[now].x]) Q.emplace(par[now].x);
	}

	for(int k = 1; k <= n; k++) if(deg[k]) {
		int p = k;
		vector<pll> cyc;
		deque<pll> Q;
		while(deg[p]) {
			deg[p]--;
			cyc.emplace_back(p, par[p].y);
			p = par[p].x;
		}
		long long ret = 0, dis = cyc[0].y, pdis = 0;
		for(pll v : cyc) ret = max(ret, max(dm[v.x], dp[v.x].x + dp[v.x].y));
		for(int i = 1; i < cyc.size(); i++) {
			while(!Q.empty() && Q.back().x < dis + dp[cyc[i].x].x) Q.pop_back();
			Q.emplace_back(dis +  dp[cyc[i].x].x, i);
			dis += cyc[i].y;
		}
		ret = max(ret, dp[cyc[0].x].x + Q.front().x);
		for(int i = 0; i < cyc.size() - 1; i++) {
			if(Q.front().y == i + 1) Q.pop_front();
			while(!Q.empty() && Q.back().x < dis + dp[cyc[i].x].x) Q.pop_back();
			Q.emplace_back(dis + dp[cyc[i].x].x, i);
			dis += cyc[i].y;
			pdis += cyc[i].y;
			ret = max(ret, dp[cyc[i + 1].x].x + Q.front().x - pdis);
		}

		ans += ret;
	}

	printf("%lld", ans);

	return 0;
}

Compilation message (stderr)

islands.cpp: In function 'int main()':
islands.cpp:48:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i = 1; i < cyc.size(); i++) {
                  ~~^~~~~~~~~~~~
islands.cpp:54:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i = 0; i < cyc.size() - 1; i++) {
                  ~~^~~~~~~~~~~~~~~~
islands.cpp:17:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
  ~~~~~^~~~~~~~~~
islands.cpp:20:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%lld%lld", &v, &w);
   ~~~~~^~~~~~~~~~~~~~~~~~~~

• 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: 10 / 10