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Submission #262188

# Submission time Handle Problem Language Result Execution time Memory
262188 2020-08-12T12:57:59 Z dantoh000 Islands (IOI08_islands) C++14
90 / 100
 1200 ms 131076 KB 
#include <bits/stdc++.h>
#define fi first
#define se second
///Input format is not always nice, first nodes may not be in the keychain ring
using namespace std;
typedef long long ll;
typedef pair<int,int> ii;
typedef pair<ll, int> li;
int n;
vector<ii> G[1000005];
ll P[1000005];
int D[1000005];
int Pct;
short vis[1000005];
ll ANS;
ll ans;
int cyclehead;
void dfs(int u, int p){
    vis[u] = 2;
    int join =0;

    int ct = 0;
    for (auto v: G[u]){

        if (vis[v.fi] & 2){
            if (v.fi == p){
                if (ct == 1){
                    cyclehead = p;
                    //printf("%d %d repeated\n",u,v.fi);
                    vis[u] |= 4;
                    join = v.se;
                }
                else {
                    ct++;
                }
                continue;
            }
            cyclehead = v.fi;
            vis[u] |= 4;
            join = v.se;
            continue;
        }
        if (vis[v.fi]) continue;
        dfs(v.fi,u);
        if ((vis[v.fi]&4) && v.fi != cyclehead) {
            vis[u] |= 4;
            join = v.se;
            continue;
        }
    }
    if (vis[u] & 4){
        //printf("at %d : %d\n",u,join);
        P[Pct] = u;
        D[Pct] = join;
        Pct++;
    }
    vis[u] ^= 3;
}
ll dfs2(int u, int p){
    ll d2 = 0;
    ll d = 0;
    for (auto v: G[u]){
        if (v.fi == p || (vis[v.fi]&4)) continue;
        ll nd = dfs2(v.fi,u)+v.se;
        if (d <= nd){
            d2 = d;
            d = nd;
        }
        else d2 = max(d2,nd);
    }
    ans = max(ans,d2+d);
    return d;
}
ll solve(int root){
    ans = Pct = 0;
    dfs(root,-1);
    //printf("at %d\n",root);
    reverse(P,P+Pct);
    reverse(D,D+Pct);
    for (int i = 0; i < Pct; i++){
        P[i] = dfs2(P[i],-1);
        //printf("%d: %d %d\n",x.fi,d[x.fi],x.se);
    }
    if (Pct == 2){
        return max(ans,P[0]+P[1]+max(D[0],D[1]));
    }
    ll S = 0;
    ll Sl = 0;
    for (int i = 0; i < Pct; i++){
        S += D[i];
    }
    ll MX = P[0];
    ll MX2 = P[0];
    for (int i = 1; i < Pct; i++){
        ll x = P[i];
        //printf("at %lld %lld\n",d[x],Sl[x]);
        //printf("MX: %lld + %lld\n",MX,d[x] + Sl[x]);
        //printf("MX2: %lld + %lld\n",MX2,S + d[x] - Sl[x]);
        Sl += D[i-1];
        ans = max(ans, x + Sl + MX);
        ans = max(ans, S + x - Sl + MX2);
        MX = max(MX, x - Sl);
        MX2 = max(MX2, x + Sl);
    }
    //printf("%lld max\n",ans);
    return ans;
}
int main(){
    scanf("%d",&n);
    for (int i = 1; i <= n; i++){
        int j,L;
        scanf("%d%d",&j,&L);
        G[i].push_back({j,L});
        G[j].push_back({i,L});
    }
    for (int i = 1; i <= n; i++){
        if (vis[i] == 0){
            ANS += solve(i);
        }
    }
    printf("%lld",ANS);
}

Compilation message

islands.cpp: In function 'int main()':
islands.cpp:109:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  109 |     scanf("%d",&n);
      |     ~~~~~^~~~~~~~~
islands.cpp:112:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  112 |         scanf("%d%d",&j,&L);
      |         ~~~~~^~~~~~~~~~~~~~

Subtask #1
33.0 / 33.0

# Verdict Execution time Memory Grader output
1 Correct 16 ms 23808 KB Output is correct
2 Correct 17 ms 23808 KB Output is correct
3 Correct 16 ms 23808 KB Output is correct
4 Correct 16 ms 23808 KB Output is correct
5 Correct 15 ms 23808 KB Output is correct
6 Correct 15 ms 23808 KB Output is correct
7 Correct 15 ms 23808 KB Output is correct
8 Correct 15 ms 23808 KB Output is correct
9 Correct 16 ms 23808 KB Output is correct
10 Correct 17 ms 23808 KB Output is correct
11 Correct 15 ms 23936 KB Output is correct

Subtask #2
3.0 / 3.0

# Verdict Execution time Memory Grader output
1 Correct 15 ms 23968 KB Output is correct
2 Correct 15 ms 23808 KB Output is correct

Subtask #3
4.0 / 4.0

# Verdict Execution time Memory Grader output
1 Correct 16 ms 23936 KB Output is correct
2 Correct 21 ms 24192 KB Output is correct

Subtask #4
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 25 ms 24704 KB Output is correct
2 Correct 35 ms 26636 KB Output is correct
3 Correct 27 ms 24696 KB Output is correct
4 Correct 21 ms 24192 KB Output is correct

Subtask #5
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 43 ms 27512 KB Output is correct
2 Correct 60 ms 29212 KB Output is correct

Subtask #6
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 133 ms 33340 KB Output is correct
2 Correct 117 ms 38392 KB Output is correct
3 Correct 174 ms 47204 KB Output is correct

Subtask #7
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 189 ms 40212 KB Output is correct
2 Correct 235 ms 61688 KB Output is correct
3 Correct 261 ms 67448 KB Output is correct
4 Correct 346 ms 83832 KB Output is correct

Subtask #8
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 427 ms 64976 KB Output is correct
2 Correct 936 ms 108408 KB Output is correct
3 Correct 356 ms 56164 KB Output is correct
4 Correct 471 ms 89976 KB Output is correct
5 Correct 453 ms 90744 KB Output is correct
6 Correct 1200 ms 61176 KB Output is correct
7 Correct 504 ms 116600 KB Output is correct

Subtask #9
0 / 10.0

# Verdict Execution time Memory Grader output
1 Runtime error 488 ms 131076 KB Execution killed with signal 9 (could be triggered by violating memory limits)
2 Halted 0 ms 0 KB -