Submission #89905

#	Time	Username	Problem	Language	Result	Execution time	Memory
89905		psmao	Islands (IOI08_islands)	C++14	100 / 100	587 ms	90168 KiB

islands

#include <bits/stdc++.h>
using namespace std;

#define fo(i,s,t) for(int i = s; i <= t; ++ i)
#define fd(i,s,t) for(int i = s; i >= t; -- i)
#define bf(i,s) for(int i = head[s]; i; i = e[i].next)
#define mp make_pair
#define fi first
#define se second
#define pii pair<int,int>
#define pb push_back
#define VI vector<int>
#define sf scanf
#define pf printf
#define fp freopen
#define SZ(x) ((int)(x).size())
#ifdef MPS
#define D(x...) printf(x)
#else
#define D(x...)
#endif
typedef long long ll;
typedef double db;
typedef unsigned long long ull;
const int inf = 1<<30;
const ll INF = 1ll<<60;
const db Inf = 1e20;
const db eps = 1e-9;

void gmax(int &a,int b){a = (a > b ? a : b);}
void gmin(int &a,int b){a = (a < b ? a : b);}

const int maxn = 1000001;

int n, deg[maxn];
ll Ans, dm[maxn];
pii adj[maxn];
pair<ll,ll> dp[maxn];

ll solve(int x)
{
	deque<pair<ll,int> > Q;
	vector<pair<int,ll> > V; V.emplace_back(mp(0,0ll));
	int sz = 0; ll ret = 0;

	while(deg[x])
	{
		-- deg[x];
		V.pb(mp(x, adj[x].se));
		dm[x] = max(dm[x], dp[x].fi + dp[x].se);
		ret = max(ret, dm[x]);
		x = adj[x].fi;
		++ sz;
	}
	fo(i,1,sz) V[i].se += V[i-1].se;
	fo(i,2,sz)
	{
		while(SZ(Q) && Q.back().fi < V[i-1].se + dp[V[i].fi].fi) Q.pop_back();
		Q.emplace_back(mp(V[i-1].se + dp[V[i].fi].fi, V[i].fi));
	}
	ret = max(ret, dp[V[1].fi].fi + Q.front().fi);
	fo(i,1,sz-1)
	{
		if(Q.front().se == V[i+1].fi) Q.pop_front();
		while(SZ(Q) && Q.back().fi < V[sz].se + V[i-1].se + dp[V[i].fi].fi) Q.pop_back();
		Q.emplace_back(mp(V[sz].se+V[i-1].se+dp[V[i].fi].fi, V[i].fi));
		ret = max(ret, Q.front().fi + dp[V[i+1].fi].fi - V[i].se);
	}
	return ret;
}
int main()
{
	sf("%d",&n);
	fo(i,1,n) {int u, v; sf("%d%d",&u,&v); deg[u] ++; adj[i] = (mp(u, v));}
	queue<int> Q;
	fo(i,1,n) if(!deg[i]) Q.push(i);
	while(!Q.empty())
	{
		int h = Q.front(); Q.pop();
		pii p = adj[h];
		dm[h] = max(dm[h], dp[h].fi + dp[h].se);
		dm[p.fi] = max(dm[p.fi], dm[h]);
		ll x = dp[h].fi + p.se;
		if(x > dp[p.fi].fi) swap(x, dp[p.fi].fi);
		if(x > dp[p.fi].se) swap(x, dp[p.fi].se);
		if(!(--deg[p.fi])) Q.push(p.fi);
	}
	fo(i,1,n) if(deg[i]) Ans += solve(i);
	cout << Ans << endl;
	return 0;
}

Compilation message (stderr)

islands.cpp: In function 'int main()':
islands.cpp:73:4: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  sf("%d",&n);
    ^
islands.cpp:74:25: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  fo(i,1,n) {int u, v; sf("%d%d",&u,&v); deg[u] ++; adj[i] = (mp(u, v));}
                         ^

• 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