Submission #201186

#	Time	Username	Problem	Language	Result	Execution time	Memory
201186		a_player	Islands (IOI08_islands)	C++14	70 / 100	659 ms	131076 KiB

islands

#include <bits/stdc++.h>
#define f first
#define s second.first
#define tr second.second
#define mp make_pair

using namespace std;


//ofstream out("output.txt");

const int MAXN =1e6+1;
typedef long long ll;

int read(){
    int r=0;
    char ch=getchar();
    while(ch<'0'||ch>'9')ch=getchar();
    r=ch-'0';
    ch=getchar();
    while(ch>='0'&&ch<='9'){
        r=r*10+ch-'0';
        ch=getchar();
    }
    return r;
}

vector<pair<int,pair<ll,int> > > grafo[MAXN];
map<int,ll> m[4];
deque<int> cyc;
map<int,ll> succ;
bitset<MAXN> v;
bitset<MAXN> k;
map<int,ll> zipp;
int pos[MAXN];
bool find_cyc(int n, int pa){
    v[n]=1;
    k[n]=1;
    cyc.push_back(n);
    for(auto x:grafo[n]){
        if(!v[x.f]){
        if(find_cyc(x.f,x.tr))return true;
        }
        else if(x.tr!=pa){
            cyc.push_back(x.f);
            return true;
        }
    }
    cyc.pop_back();
    return false;
}
ll zip(int n, int a, int b, int c){
    k[n]=1;
    ll mas=0;
    for(auto x:grafo[n]){
        if(x.f==a||x.f==b||x.f==c)continue;
        mas=max(mas,zip(x.f,n,b,c)+x.s);
    }
    return mas;
}
ll dfs(int n, int a){
    ll mas=0;
    pos[n]=-1;
    k[n]=1;
    for(auto x:grafo[n]){
        if(n==cyc.front()&&x.f==cyc.back())continue;
        if(x.f==cyc.front()&&n==cyc.back())continue;
        if(x.f==a)continue;
        ll p=dfs(x.f,n)+x.s;
        if(mas<p){
            mas=p;
            pos[n]=pos[x.f];
        }
    }
    if(pos[n]==-1)pos[n]=n;
    return mas;
}
ll dfs2(int n, int a, int w){
    ll mas=0;
    pos[n]=-1;
    k[n]=1;
    for(auto x:grafo[n]){
        if(n==cyc.front()&&x.f==cyc.back()&&x.s!=w)continue;
        if(x.f==cyc.front()&&n==cyc.back()&&x.s!=w)continue;
        if(x.f==a)continue;
        ll p=dfs2(x.f,n,w)+x.s;
        if(mas<p){
            mas=p;
            pos[n]=pos[x.f];
        }
    }
    if(pos[n]==-1)pos[n]=n;
    return mas;
}
int N;
ll process(int t){
    cyc.clear();
    find_cyc(t,-1);
    while(cyc.front()!=cyc.back())cyc.pop_front();
    cyc.pop_front();
    zipp[cyc[0]]=zip(cyc[0],-1,cyc[1],cyc.back());
    for(int i=1;i<cyc.size()-1;i++)zipp[cyc[i]]=zip(cyc[i],-1,cyc[i-1],cyc[i+1]);
    zipp[cyc.back()]=zip(cyc.back(),-1,cyc[cyc.size()-2],cyc.front());
    if(cyc.size()==2){
        ll mass=0;
    for(auto x:grafo[cyc[0]])
    if(x.f==cyc[1]){
        mass=max(mass,x.s);
    }
    dfs2(t,-1,mass);
    return dfs2(pos[t],-1,mass);
    }
    for(int i=1;i<cyc.size()-1;i++)
    for(auto x:grafo[cyc[i]])
    if(x.f==cyc[i+1]){
        succ[cyc[i]]=x.s;
        break;
    }
    ll speciale=0;
    for(auto x:grafo[cyc[0]]){
        if(x.f==cyc[1])succ[cyc[0]]=x.s;
        if(x.f==cyc.back())speciale=x.s;
    }
    int se=cyc.size();
    m[0][cyc[0]]=0;
    for(int i=1;i<se;i++)m[0][cyc[i]]=m[0][cyc[i-1]]+succ[cyc[i-1]];
    m[1][cyc[0]]=zipp[cyc[0]];
    for(int i=1;i<se;i++)m[1][cyc[i]]=max(m[1][cyc[i-1]],m[0][cyc[i]]+zipp[cyc[i]]);
    m[2][cyc.back()]=0;
    for(int i=se-2;i>=0;i--)m[2][cyc[i]]=m[2][cyc[i+1]]+succ[cyc[i]];
    m[3][cyc.back()]=zipp[cyc.back()];
    for(int i=se-2;i>=0;i--)m[3][cyc[i]]=max(m[3][cyc[i+1]],m[2][cyc[i]]+zipp[cyc[i]]);
    
    ll ans=0;
    for(int i=0;i<se-1;i++)ans=max(ans,m[1][cyc[i]]+m[3][cyc[i+1]]+speciale);
    dfs(t,-1);
    ans=max(ans,dfs(pos[t],-1));
    return ans;
}
int main(){
    //freopen("input.txt","r",stdin);
    N=read();
    for(int i=0;i<N;i++){
        int a,c;
        a=read(),c=read();
        a--;
        grafo[a].push_back(mp(i,mp((ll)c,i)));
        grafo[i].push_back(mp(a,mp((ll)c,i)));
    }
    ll ans=0;
    for(int i=0;i<N;i++)
    if(!k[i])ans+=process(i);
    cout<<ans;

}

Compilation message (stderr)

islands.cpp: In function 'll process(int)':
islands.cpp:102:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=1;i<cyc.size()-1;i++)zipp[cyc[i]]=zip(cyc[i],-1,cyc[i-1],cyc[i+1]);
                 ~^~~~~~~~~~~~~
islands.cpp:113:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=1;i<cyc.size()-1;i++)
                 ~^~~~~~~~~~~~~

• 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