Submission #1055426

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
1055426	2024-08-12T19:12:28 Z	MilosMilutinovic	Islands (IOI08_islands)	C++14	90 / 100	544 ms	131072 KB

islands

#include <bits/stdc++.h>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  vector<int> a(n), l(n);
  for (int i = 0; i < n; i++) {
    cin >> a[i] >> l[i];
    --a[i];
  }
  vector<vector<int>> g(n);
  for (int i = 0; i < n; i++) {
    g[i].push_back(a[i]);
    g[a[i]].push_back(i);
  }
  vector<bool> was(n);
  long long res = 0;
  vector<long long> d(n, -1);
  vector<long long> dp(n);
  for (int i = 0; i < n; i++) {
    if (was[i]) {
      continue;
    }
    vector<int> que(1, i);
    for (int b = 0; b < (int) que.size(); b++) {
      int x = que[b];
      for (int y : g[x]) {
        if (!was[y]) {
          was[y] = true;
          que.push_back(y);
        }
      }
    }
    for (int x : que) {
      was[x] = false;
    }
    int x = i;
    while (!was[x]) {
      was[x] = true;
      x = a[x];
    }
    int y = a[x];
    vector<int> cyc(1, x);
    while (y != x) {
      cyc.push_back(y);
      y = a[y];
    }
    for (int x : que) {
      was[x] = true;
    }
    d[cyc[0]] = 0;
    for (int i = 1; i < (int) cyc.size(); i++) {
      int x = cyc[i - 1], y = cyc[i];
      d[y] = d[x] + l[x];
    }
    vector<int>().swap(que);
    long long c = 0;
    function<void(int, int)> Solve = [&](int v, int pv) {
      for (int u : g[v]) {
        if (d[u] != -1 || u == pv) {
          continue;
        }
        Solve(u, v);
        c = max(c, dp[v] + dp[u] + l[u]);
        dp[v] = max(dp[v], dp[u] + l[u]);
      }
    };
    for (int i : cyc) {
      Solve(i, i);
      c = max(c, dp[i]);
    }
    int sz = (int) cyc.size();
    vector<vector<long long>> mx(sz, vector<long long>(2, -(long long) 1e18));
    for (int i = sz - 1; i >= 0; i--) {
      if (i + 1 < sz) {
        mx[i] = mx[i + 1];
      }
      mx[i][0] = max(mx[i][0], d[cyc[i]] + dp[cyc[i]]);
      mx[i][1] = max(mx[i][1], -d[cyc[i]] + dp[cyc[i]]);
    }
    long long t = d[cyc.back()] + l[cyc.back()];
    for (int i = 0; i < sz; i++) {
      int low = i + 1, high = sz - 1, pos = i;
      while (low <= high) {
        int mid = (low + high) >> 1;
        if (t - (d[cyc[mid]] - d[cyc[i]]) >= (d[cyc[mid]] - d[cyc[i]])) {
          pos = mid;
          low = mid + 1;
        } else {
          high = mid - 1;
        }
      }
      if (pos + 1 < sz) {
        c = max(c, -d[cyc[i]] + dp[cyc[i]] + mx[pos + 1][0]);
      }
      if (pos > i) {
        c = max(c, t + d[cyc[i]] + dp[cyc[i]] + mx[i + 1][1]);
      }
    }
    res += c;
  }
  cout << res << '\n';
  return 0;
}

Subtask #1
33.0 / 33.0

#	Verdict	Memory	Grader output
1	Correct	344 KB	Output is correct
2	Correct	348 KB	Output is correct
3	Correct	348 KB	Output is correct
4	Correct	348 KB	Output is correct
5	Correct	348 KB	Output is correct
6	Correct	348 KB	Output is correct
7	Correct	348 KB	Output is correct
8	Correct	348 KB	Output is correct
9	Correct	348 KB	Output is correct
10	Correct	344 KB	Output is correct
11	Correct	348 KB	Output is correct

Subtask #2
3.0 / 3.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	0 ms	348 KB	Output is correct
2	Correct	1 ms	348 KB	Output is correct

Subtask #3
4.0 / 4.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	1 ms	604 KB	Output is correct
2	Correct	1 ms	860 KB	Output is correct

Subtask #4
10.0 / 10.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	4 ms	1628 KB	Output is correct
2	Correct	9 ms	3916 KB	Output is correct
3	Correct	7 ms	2156 KB	Output is correct
4	Correct	2 ms	1372 KB	Output is correct

Subtask #5
10.0 / 10.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	12 ms	5468 KB	Output is correct
2	Correct	20 ms	9332 KB	Output is correct

Subtask #6
10.0 / 10.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	39 ms	17492 KB	Output is correct
2	Correct	53 ms	23044 KB	Output is correct
3	Correct	56 ms	28788 KB	Output is correct

Subtask #7
10.0 / 10.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	76 ms	32780 KB	Output is correct
2	Correct	103 ms	51436 KB	Output is correct
3	Correct	137 ms	62628 KB	Output is correct
4	Correct	137 ms	73120 KB	Output is correct

Subtask #8
10.0 / 10.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	175 ms	88768 KB	Output is correct
2	Correct	433 ms	124016 KB	Output is correct
3	Correct	157 ms	74956 KB	Output is correct
4	Correct	203 ms	109356 KB	Output is correct
5	Correct	222 ms	108972 KB	Output is correct
6	Correct	544 ms	95940 KB	Output is correct
7	Correct	286 ms	129524 KB	Output is correct

Subtask #9
0 / 10.0

#	Verdict	Execution time	Memory	Grader output
1	Runtime error	213 ms	131072 KB	Execution killed with signal 9
2	Halted	0 ms	0 KB	-

Submission #1055426

Compilation message