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Submission #53888

# Submission time Handle Problem Language Result Execution time Memory
53888 2018-07-01T14:21:21 Z Diuven Islands (IOI08_islands) C++11
100 / 100
 1779 ms 206600 KB 
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, ll> pil;
const int MX=1000010;
const ll inf=2e17;

int n, A[MX], C[MX];
vector<pil> G[MX];
bool done[MX];

ll D[MX];

bool vis[MX];

// list all vertices
void dfs1(int v, vector<int> &V){
    done[v]=true;
    V.push_back(v);
    for(pil &e:G[v]){
        int x=e.first;
        if(done[x]) continue;
        dfs1(x,V);
    }
}

// find cycle 
int found=-1;
int dep[MX], now;
void dfs2(int v, int p, vector<int> &V){
    dep[v]=++now;
    for(pil &e:G[v]){
        int x; ll c; tie(x,c)=e;
        if(p==x) continue;
        if(dep[x]>=0)
            found=x;
        else
            dfs2(x,v,V);
        if(found>=0){
            if(dep[v]>=dep[found]) V.push_back(v);
            return;
        }
    }
    --now;
}

// farthest point
ll dist[MX]; 
int dfs3(int v){
    int res=v;
    for(pil &e:G[v]){
        int x; ll c; tie(x,c)=e;
        if(dist[x]>=0) continue;
        dist[x]=dist[v]+c;
        int y=dfs3(x);
        if(dist[y]>dist[res]) res=y;
    }
    return res;
}
ll solve_tree(vector<int> &V){
    int s=V[0];

    for(int v:V) dist[v]=-1;
    dist[s]=0;
    int u=dfs3(s);

    for(int v:V) dist[v]=-1;
    dist[u]=0;
    int v=dfs3(u);

    return dist[v];
}

bool incyc[MX];
ll arm[MX], scd[MX];
// longest path from v in cyc
void dfs4(int v){
    arm[v]=0;
    for(pil &e:G[v]){
        int x; ll c; tie(x,c)=e;
        if(incyc[x] || arm[x]>=0) continue;
        dfs4(x);
        ll now=arm[x]+c;
        scd[v]=max(scd[v], now);
        if(scd[v]>arm[v]) swap(scd[v], arm[v]);
    }
}

ll Val[2*MX], Len[2*MX], Sum[2*MX];

vector<int> V, cyc;
ll solve(int s){
    // cout<<"\nSOLVE ON "<<s<<'\n';
    V.clear(), cyc.clear();
    dfs1(s, V);

    found=-1, now=0;
    for(int v:V) dep[v]=-1;
    dfs2(s, -1, cyc);

    if(cyc.empty())
        return solve_tree(V);

    ll res=0;

    for(int v:V) arm[v]=-1, scd[v]=0;
    for(int v:cyc) incyc[v]=true, arm[v]=0;
    for(int v:cyc) dfs4(v);
    for(int v:V) res=max(res, arm[v]+scd[v]);

    int sz=cyc.size();
    Sum[0]=0;
    for(int i=0; i<sz; i++){
        int v=cyc[i];
        Val[i]=arm[v];
        int nxt=cyc[(i+1)%sz];
        for(pil &e:G[v])
            if(e.first==nxt) Len[i]=e.second;
        Sum[i+1]=Sum[i]+Len[i];
    }
    for(int i=sz; i<2*sz; i++)
        Sum[i]=Sum[i%sz]+Sum[sz];
    deque<int> Q;
    for(int j=0; j<=2*sz-1; j++){
        int i=j%sz;
        while(!Q.empty() && Q.front()<=j-sz) Q.pop_front();
        if(!Q.empty()){
            int x=Q.front();
            ll now=Val[x%sz] + Val[i] + Sum[j]-Sum[x];
            res=max(res, now);
        }
        while(!Q.empty()){
            int x=Q.back();
            ll a=Val[x%sz]-Sum[x];
            ll b=Val[j%sz]-Sum[j];
            if(a<=b) Q.pop_back();
            else break;
        }
        Q.push_back(j);
    }
    return res;
    for(int i=0; i<sz; i++)
        for(int j=i+1; j<sz; j++){
            ll dist=max(Sum[j]-Sum[i], Sum[sz]+Sum[i]-Sum[j]);
            ll now=dist+Val[i]+Val[j];

            // printf("%d - %d : %lld (%lld)\n", cyc[i], cyc[j], now, dist);
            res=max(res, now);
        }
    return res;
}

int main(){
    ios::sync_with_stdio(0); cin.tie(0);
    cin>>n;
    for(int u=1; u<=n; u++){
        int v, c; cin>>v>>c;
        A[u]=v, C[u]=c;
        if(v<u && A[v]==u){
            C[u]=max(C[u], C[v]);
            C[v]=-1;
        }
    }
    for(int i=1; i<=n; i++){
        if(C[i]<0) continue;
        G[i].push_back({A[i], C[i]});
        G[A[i]].push_back({i, C[i]});
    }
    ll ans=0;
    for(int i=1; i<=n; i++){
        if(done[i]) continue;
        ans+=solve(i);
    }
    cout<<ans;
    return 0;
}

Subtask #1
33.0 / 33.0

# Verdict Execution time Memory Grader output
1 Correct 31 ms 23928 KB Output is correct
2 Correct 25 ms 23928 KB Output is correct
3 Correct 20 ms 24116 KB Output is correct
4 Correct 21 ms 24116 KB Output is correct
5 Correct 22 ms 24116 KB Output is correct
6 Correct 20 ms 24156 KB Output is correct
7 Correct 22 ms 24172 KB Output is correct
8 Correct 21 ms 24172 KB Output is correct
9 Correct 21 ms 24188 KB Output is correct
10 Correct 21 ms 24188 KB Output is correct
11 Correct 21 ms 24192 KB Output is correct

Subtask #2
3.0 / 3.0

# Verdict Execution time Memory Grader output
1 Correct 23 ms 24316 KB Output is correct
2 Correct 23 ms 24316 KB Output is correct

Subtask #3
4.0 / 4.0

# Verdict Execution time Memory Grader output
1 Correct 23 ms 24316 KB Output is correct
2 Correct 24 ms 24700 KB Output is correct

Subtask #4
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 35 ms 25584 KB Output is correct
2 Correct 49 ms 28920 KB Output is correct
3 Correct 36 ms 28920 KB Output is correct
4 Correct 29 ms 28920 KB Output is correct

Subtask #5
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 55 ms 30524 KB Output is correct
2 Correct 66 ms 34168 KB Output is correct

Subtask #6
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 125 ms 42988 KB Output is correct
2 Correct 142 ms 49908 KB Output is correct
3 Correct 167 ms 61124 KB Output is correct

Subtask #7
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 200 ms 61124 KB Output is correct
2 Correct 280 ms 87520 KB Output is correct
3 Correct 310 ms 97828 KB Output is correct
4 Correct 387 ms 119232 KB Output is correct

Subtask #8
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 452 ms 119232 KB Output is correct
2 Correct 1328 ms 164496 KB Output is correct
3 Correct 397 ms 164496 KB Output is correct
4 Correct 564 ms 164496 KB Output is correct
5 Correct 541 ms 164496 KB Output is correct
6 Correct 1616 ms 164496 KB Output is correct
7 Correct 597 ms 171088 KB Output is correct

Subtask #9
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 649 ms 171088 KB Output is correct
2 Correct 639 ms 171088 KB Output is correct
3 Correct 690 ms 206600 KB Output is correct
4 Correct 374 ms 206600 KB Output is correct
5 Correct 528 ms 206600 KB Output is correct
6 Correct 486 ms 206600 KB Output is correct
7 Correct 1779 ms 206600 KB Output is correct