Submission #1038048

#	Time	Username	Problem	Language	Result	Execution time	Memory
1038048		8pete8	Islands (IOI08_islands)	C++17	65 / 100	709 ms	125192 KiB

islands

#include<iostream>
#include<stack>
#include<map>
#include<vector>
#include<string>
#include<cassert>
#include<unordered_map>
#include <queue>
#include <cstdint>
#include<cstring>
#include<limits.h>
#include<cmath>
#include<set>
#include<algorithm>
#include <iomanip>
#include<numeric>
#include<bitset>
using namespace std;
#define ll long long
#define f first
#define s second
#define pii pair<int,int>
#define ppii pair<int,pii>
#define vi vector<int>
#define pb push_back
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define F(n) for(int i=0;i<n;i++)
#define lb lower_bound
#define ub upper_bound
#define fastio ios::sync_with_stdio(false);cin.tie(NULL);
#pragma GCC optimize ("03,unroll-lopps")
//#define int long long
using namespace std;
const int mod=1e9+7,mxn=1e6+5,inf=1e9,minf=-1e9,lg=25;
int n,m,k,x,y,z=0;
vector<pair<int,ll>>adj[mxn+10];
int have=0,pointer=0;
int up[mxn+10],dup[mxn+10];
pii cycle[mxn+10];
ll dp1[mxn+10],mx,suf[mxn+10];
//8^106
bitset<mxn+10>on,vis;
ll ans=0,pref=0,prefmx=0;
queue<pii>q;
map<pii,int>mp;
ll m1=0,m2=0;
void dfs(int cur,int p){//fake dfs
    q.push({cur,-1});
    while(!q.empty()){
        cur=q.front().f,p=q.front().s;
        q.pop();
        if(vis[cur])continue;
        vis[cur]=1;
        for(auto i:adj[cur]){
            if(i.f==p)continue;
            if(vis[i.f]&&!have){
                x=cur,y=i.f,z=i.s;
                have++;
            }
            if(!vis[i.f])q.push({i.f,cur});
        }
    }
}
void dfs1(int cur,int p){//dont take edge x,y
    q.push({cur,-1});
    while(!q.empty()){
        cur=q.front().f,p=q.front().s;
        q.pop();
        for(auto i:adj[cur]){
            if(i.f==p)continue;
            if(cur==x&&i.f==y)continue;
            if(cur==y&&i.f==x)continue;
            up[i.f]=cur;
            dup[i.f]=i.s;
            dp1[i.f]=dp1[cur]+1;
            q.push({i.f,cur});
        }
        cycle[pointer++]={dp1[cur],cur};
        dp1[cur]=0;
    }
}
//find diameter 
int32_t main(){
    fastio
    cin>>n;
    for(int i=1;i<=n;i++){
        int a,b;cin>>a>>b;
        adj[a].pb({i,b});
        adj[i].pb({a,b});
        /*
        pii x={min(a,i),max(a,i)};
        if(mp.find(x)==mp.end())mp[x]=b;
        else mp[x]=max(mp[x],b);*/
    }
    /*
    for(auto i:mp){
        adj[i.f.f].pb({i.f.s,i.s});
        adj[i.f.s].pb({i.f.f,i.s});
    }*/
    for(int i=1;i<=n;i++){
        if(vis[i])continue;
        have=0,z=0,x=i,mx=0;
        dfs(i,-1);
        pointer=0;
        dfs1(x,-1);
        sort(cycle,cycle+pointer);
        reverse(cycle,cycle+pointer);
        for(int j=0;j<pointer;j++){
            dp1[up[cycle[j].s]]=max(dp1[up[cycle[j].s]],dp1[cycle[j].s]+dup[cycle[j].s]);
            mx=max(mx,dp1[cycle[j].s]);
            m1=m2=0;
            for(auto k:adj[cycle[j].s]){
                if(k.f==up[cycle[j].s])continue;
                if(cycle[j].s==x&&k.f==y)continue;
                if(cycle[j].s==y&&k.f==x)continue;
                if(dp1[k.f]+k.s>=m1)m2=m1,m1=dp1[k.f]+k.s;
                else if(dp1[k.f]+k.s>=m2)m2=dp1[k.f]+k.s;
            }
            mx=max(mx,m1+m2);
        }
        if(have){
            pointer=0;
            while(y!=x){
                cycle[pointer++]={y,dup[y]};
                on[y]=1;
                y=up[y];
            }
            cycle[pointer++]={x,0};
            on[x]=1;
            reverse(cycle,cycle+pointer);
            suf[pointer-1]=0;
            pref=0,prefmx=0;
            for(int i=pointer-2;i>=0;i--)suf[i]=cycle[i+1].s+suf[i+1];
            for(int i=0;i<pointer;i++){
                dp1[cycle[i].f]=0;
                for(auto j:adj[cycle[i].f])if(!on[j.f])dp1[cycle[i].f]=max(dp1[cycle[i].f],dp1[j.f]+j.s);
            }
            for(int i=pointer-1;i>=0;i--){
                suf[i]=suf[i]+dp1[cycle[i].f];
                if(i+1<pointer)suf[i]=max(suf[i],suf[i+1]);
            }
            for(int i=0;i<pointer;i++){
                pref+=cycle[i].s;
                prefmx=max(prefmx,pref+dp1[cycle[i].f]);
                if(i+1<pointer)mx=max(mx,prefmx+suf[i+1]+z);
            }
        }
        ans+=mx;
    }
    cout<<ans<<'\n';
}

Compilation message (stderr)

islands.cpp:32:40: warning: bad option '-funroll-lopps' to pragma 'optimize' [-Wpragmas]
   32 | #pragma GCC optimize ("03,unroll-lopps")
      |                                        ^
islands.cpp:48:23: warning: bad option '-funroll-lopps' to attribute 'optimize' [-Wattributes]
   48 | void dfs(int cur,int p){//fake dfs
      |                       ^
islands.cpp:65:24: warning: bad option '-funroll-lopps' to attribute 'optimize' [-Wattributes]
   65 | void dfs1(int cur,int p){//dont take edge x,y
      |                        ^
islands.cpp:84:14: warning: bad option '-funroll-lopps' to attribute 'optimize' [-Wattributes]
   84 | int32_t main(){
      |              ^

• Subtask 1: 15 / 33
• Subtask 2: 0 / 3
• Subtask 3: 0 / 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