Submission #304591

#	Time	Username	Problem	Language	Result	Execution time	Memory
304591		rocks03	Islands (IOI08_islands)	C++14	0 / 100	18 ms	23968 KiB

islands

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pld pair<long double, int>
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pb push_back
#define ff first
#define ss second
#define SZ(x) ((int)(x).size())
#define ld long double
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

const int MAXN = 1e6+100;
int N;
vector<pii> adj[MAXN];

void read(){
    cin >> N;
    for(int i = 0; i < N; i++){
        int u, w;
        cin >> u >> w;
        --u;
        adj[i].pb({u, w});
        adj[u].pb({i, w});
    }
}

bool vis[MAXN], vis2[MAXN];
vector<int> componente;

void dfs(int v){
    vis[v] = true;
    componente.pb(v);
    for(auto u : adj[v]){
        if(!vis[u.ff]){
            dfs(u.ff);
        }
    }
}

ll dfs2(int v){
    ll ans = 0;
    vis2[v] = true;
    for(auto u : adj[v]){
        if(!vis2[u.ff]){
            ans = max(ans, dfs2(u.ff) + u.ss);
        }
    }
    vis2[v] = false;
    return ans;
}

void solve(){
    read();
    ll ans = 0;
    for(int i = 0; i < N; i++){
        if(!vis[i]){
            dfs(i);
            ll res = 0;
            for(auto v : componente){
                res = max(res, dfs2(v));
            }
            ans += res;
            componente.clear();
        }
    }
    cout << ans;
}

int main(){
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    solve();
    return 0;
}

Compilation message (stderr)

islands.cpp: In function 'int main()':
islands.cpp:72:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   72 |     freopen("input.txt", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
islands.cpp:73:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   73 |     freopen("output.txt", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 33
• Subtask 2: 0 / 3
• Subtask 3: 0 / 4
• Subtask 4: 0 / 10
• Subtask 5: 0 / 10
• Subtask 6: 0 / 10
• Subtask 7: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10