Submission #992479

#	Time	Username	Problem	Language	Result	Execution time	Memory
992479		PedroBigMan	Islands (IOI08_islands)	C++14	70 / 100	340 ms	131072 KiB

islands

#pragma GCC optimization ("O3")
#pragma GCC optimization ("unroll-loops")
#pragma GCC optimize("Ofast")
#include <iostream>
#include <vector>
#include <cmath>
#include <algorithm>
#include <string>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <queue>
#include <deque>
#include <list>
#include <iomanip>
#include <stdlib.h>
#include <time.h>
#include <cstring>
using namespace std;
typedef long long int ll;
typedef unsigned long long int ull;
typedef long double ld;
#define REP(i,a,b) for(ll i=(ll) a; i<(ll) b; i++)
#define pb push_back
#define mp make_pair
#define pl pair<ll,ll>
#define ff first
#define ss second
#define whole(x) x.begin(),x.end()
#define DEBUG(i) cout<<"Pedro "<<i<<endl
#define INF 1000000000000000000LL
#define EPS ((ld)0.00000000001)
#define pi ((ld)3.141592653589793)
#define VV(vvvv,NNNN,xxxx); REP(iiiii,0,NNNN) {vvvv.pb(xxxx);}
ll mod=1000000007;

template<class A=ll> 
void Out(vector<A> a) {REP(i,0,a.size()) {cout<<a[i]<<" ";} cout<<endl;}

template<class A=ll>
void In(vector<A> &a, ll N) {A cur; REP(i,0,N) {cin>>cur; a.pb(cur);}} 

vector<ll> f, w; vector<bool> visited;
vector<vector<ll> > adj; ll nei;
ll bestpath;

vector<ll> Floyd(ll s) //Floyd's Algorithm, O(N) time, O(1) memory, return <element of cycle,length od cycle>
{
    ll a=f[s]; ll b=f[f[s]];
    while(a!=b) {a=f[a]; b=f[f[b]];}
    vector<ll> ans; ans.pb(a); b=f[a];
    while(b!=a) {ans.pb(b); b=f[b];}
    return ans;
}

ll DFS(ll s)
{
    visited[s]=true; ll ans = 0; ll thisval;
    REP(i,0,adj[s].size())
    {
        nei = adj[s][i];
        if(visited[nei]) {continue;}
        thisval = w[nei]+DFS(nei);
        bestpath = max(bestpath,ans+thisval);
        ans = max(ans,thisval);
    }
    return ans;
}

class ST
{	
    public:
    ll N;
    
    class SV //seg value
    {
        public:
        ll a; 
        SV() {a=0LL;}
        SV(ll x) {a=x;}
        
        SV operator & (SV X) {SV ANS(max(a,X.a)); return ANS;}
    };
      
    class LV //lazy value
    {
        public:
        ll a;
        LV() {a=0LL;}
        LV(ll x) {a=x;}
        
        LV operator & (LV X) {LV ANS(a+X.a); return ANS;}
    };
    
    SV upval(ll c) //how lazy values modify a seg value inside a node, c=current node
    {
        SV X(p[c].a+lazy[c].a);
        return X;
    }
    
    SV neuts; LV neutl;
    
    vector<SV> p;
    vector<LV> lazy;
    vector<pl> range;
    
    ST() {N=0LL;}
    ST(vector<ll> arr)
    {
        N = (ll) 1<<(ll) ceil(log2(arr.size()));
        REP(i,0,2*N) {range.pb(mp(0LL,0LL));}
        REP(i,0,N) {p.pb(neuts);}
        REP(i,0,arr.size()) {SV X(arr[i]); p.pb(X); range[i+N]=mp(i,i);}
        REP(i,arr.size(),N) {p.pb(neuts); range[i+N]=mp(i,i);}
        ll cur = N-1;
        while(cur>0)
        {
            p[cur]=p[2*cur]&p[2*cur+1];
            range[cur]=mp(range[2*cur].ff,range[2*cur+1].ss);
            cur--;
        }
        REP(i,0,2*N) {lazy.pb(neutl);}
    }
    
    void prop(ll c) //how lazy values propagate
    {
        p[c] = upval(c);
        lazy[2*c]=lazy[c]&lazy[2*c]; lazy[2*c+1]=lazy[c]&lazy[2*c+1];
        lazy[c]=neutl;
    }
    
    SV query(ll a,ll b, ll c=1LL) //range [a,b], current node. initially: query(a,b)
    {
		if(a>b) {return neuts;}
        ll x=range[c].ff; ll y=range[c].ss;
        if(y<a || x>b) {return neuts;}
        if(x>=a && y<=b) {return upval(c);}
        prop(c);
        SV ans = query(a,b,2*c)&query(a,b,2*c+1);
        return ans;
    }
    
    void update(LV s, ll a, ll b, ll c=1LL) //update LV, range [a,b], current node, current range. initially: update(s,a,b)
    {
		if(a>b) {return;}
        ll x=range[c].ff; ll y=range[c].ss;
        if(y<a || x>b) {return ;}
        if(x>=a && y<=b) 
        {
            lazy[c]=s&lazy[c]; 
            return;
        }
		prop(c);
        update(s,a,b,2*c); update(s,a,b,2*c+1);
        p[c]=upval(2*c)&upval(2*c+1);
    }
};



int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
	cout.precision(20);
	ll N; cin>>N; f = vector<ll>(N,-1); w = vector<ll>(N,-1); visited = vector<bool>(N,false); adj=vector<vector<ll> >(N,vector<ll>());
    REP(i,0,N) {cin>>f[i]>>w[i]; f[i]--; adj[i].pb(f[i]); adj[f[i]].pb(i);}
    ll ans = 0LL; ll node; ll C;
    REP(s,0,N)
    {
        if(visited[s]) {continue;}
        ll bestval = 0; ll thisval;
        vector<ll> cycle = Floyd(s); C = cycle.size();
        REP(i,0,cycle.size()) {node=cycle[i]; visited[node]=true;}
        vector<ll> val(C,0);
        REP(i,0,cycle.size()) 
        {
            bestpath = 0;
            val[i]=DFS(cycle[i]);
            bestval = max(bestval,bestpath);
        }
        vector<ll> ps; ll cursum=0;
        REP(i,0,2*C) {node = cycle[i%C]; ps.pb(cursum+val[i%C]); cursum+=w[node];}
        ST S(ps);
        REP(i,0,C)
        {
            thisval=S.query(i+1,i+C-1).a-(ps[i]-val[i])+val[i];
            bestval = max(thisval,bestval);
        }
        ans+=bestval;
    }
    cout<<ans<<endl;
    return 0;
}

Compilation message (stderr)

islands.cpp:1: warning: ignoring '#pragma GCC optimization' [-Wunknown-pragmas]
    1 | #pragma GCC optimization ("O3")
      | 
islands.cpp:2: warning: ignoring '#pragma GCC optimization' [-Wunknown-pragmas]
    2 | #pragma GCC optimization ("unroll-loops")
      |

• 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: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10