Submission #650699

#	Time	Username	Problem	Language	Result	Execution time	Memory
650699		Spade1	Islands (IOI08_islands)	C++14	100 / 100	344 ms	63908 KiB

islands

#include<bits/stdc++.h>
#define pii pair<int, int>
#define pll pair<long long, long long>
#define ll long long
#define ld long double
#define st first
#define nd second
#define pb push_back
#define INF INT_MAX
using namespace std;

const int N = 1e6 + 2;

pii nxt[N];
int deg[N];
bool mark[N];
ll diam[N], dist[N];
queue<int> q;
ll dp[N], qs[N];

void solve() {
    int n; cin >> n;
    for (int i = 1; i <= n; ++i) {
        int b, w; cin >> b >> w;
        nxt[i] = {b, w};
        deg[b]++;
    }

    for (int i = 1; i <= n; ++i) if (deg[i] == 0) q.push(i);
    while (!q.empty()) {
        int cur = q.front(); q.pop();
        auto [prt, w] = nxt[cur];
        diam[prt] = max(diam[prt], max(diam[cur], dist[cur]+dist[prt]+w));
        dist[prt] = max(dist[prt], dist[cur]+w);
        deg[prt]--;
        if (deg[prt] == 0) q.push(prt);
    }

    ll ans = 0;
    for (int i = 1; i <= n; ++i) {
        vector<pll> v;
        ll cur = 0;
        if (deg[i] != 0 && !mark[i]) {
            int curr = i;
            do {
                mark[curr] = 1;
                cur = max(cur, diam[curr]);
                v.pb({dist[curr], nxt[curr].nd});
                curr = nxt[curr].st;
            } while (curr != i);
        }
        else continue;

        int m = v.size();
        for (int j = 0; j <= m+1; ++j) qs[j] = 0, dp[j] = 0;
        for (int j = 1; j <= m; ++j) {
            qs[j] = qs[j-1] + v[j-1].nd;
            dp[j] = qs[j-1] + v[j-1].st;
        }
        for (int j = m-1; j > 0; --j) dp[j] = max(dp[j], dp[j+1]);
        for (int j = 1; j < m; ++j) {
            cur = max(cur, v[j-1].st - qs[j-1] + dp[j+1]);
        }
        for (int j = 0; j <= m+1; ++j) dp[j] = 0;
        for (int j = m; j >= 1; --j) {
            dp[j] = qs[j-1] + v[j-1].st;
        }
        for (int j = 2; j <= m; ++j) dp[j] = max(dp[j], dp[j-1]);
        for (int j = 2; j <= m; ++j) {
            cur = max(cur, qs[m] + v[j-1].st - qs[j-1] + dp[j-1]);
        }
        ans += cur;
    }
    cout << ans << '\n';
}

int main() {
    ios_base::sync_with_stdio(0); cin.tie(NULL);
    int t = 1;
//    cin >> t;
    while (t--) {
        solve();
    }
}

Compilation message (stderr)

islands.cpp: In function 'void solve()':
islands.cpp:32:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   32 |         auto [prt, w] = nxt[cur];
      |              ^

• 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: 10 / 10
• Subtask 8: 10 / 10
• Subtask 9: 10 / 10