Submission #1252030

#	Time	Username	Problem	Language	Result	Execution time	Memory
1252030		flashmt	Triple Peaks (IOI25_triples)	C++20	78.84 / 100	628 ms	33848 KiB

triples

#include "triples.h"
#include <bits/stdc++.h>
#ifdef LOCAL
#include "Debug.h"
#else
#define debug(...) 42
#endif
using namespace std;
const int N = 2e5 + 5;
const int K = 650;

long long calcTriangle(vector<int> h)
{
  int n = size(h);
  vector<vector<int>> a(n * 3);
  vector<pair<int, int>> edges;
  for (int i = 0; i < n * 3; i++)
    a[i].clear();
  for (int i = 0; i < n; i++)
  {
    int l = i - h[i], r = i + h[i];
    a[l + n].push_back(r + n);
    a[r + n].push_back(l + n);
    edges.push_back({l + n, r + n});
  }

  vector<int> bigId(n * 3, -1);
  int bigCnt = 0;
  for (int i = 0; i < n * 3; i++)
    if (size(a[i]) > K)
      bigId[i] = bigCnt++;

  vector<vector<int>> adj(bigCnt, vector<int>(bigCnt));
  for (auto [x, y] : edges)
    if (bigId[x] >= 0 && bigId[y] >= 0)
      adj[bigId[x]][bigId[y]] = adj[bigId[y]][bigId[x]] = 1;

  long long res = 0;
  vector<int> flag(n * 3, -1);
  for (int x = 0; x < n * 3; x++)
  {
    for (int y : a[x])
      flag[y] = x;
    vector<int> bigs;
    for (int y : a[x])
      if (bigId[y] >= 0) bigs.push_back(bigId[y]);
      else
      {
        for (int z : a[y])
          if (flag[z] == x && y < z)
            res++;
      }

    for (int i = 0; i < size(bigs); i++)
      for (int j = i + 1; j < size(bigs); j++)
        res += adj[bigs[i]][bigs[j]];
  }

  assert(res % 3 == 0);
  return res / 3;
}

long long count_triples(vector<int> h)
{
  int n = size(h);
  vector<int> l(n), r(n);
  for (int i = 0; i < n; i++)
  {
    l[i] = i - h[i];
    r[i] = i + h[i];
  }

  long long res = 0;
  for (int i = 0; i < n; i++)
  {
    int j = r[i];
    if (j < n)
    {
      // 2.3..5
      res += r[j] < n && h[r[j]] == h[i] + h[j];

      // 2.5..3
      if (h[j] > h[i])
      {
        int k = j + h[j] - h[i];
        if (k < n && l[k] == j)
          res++;
      }

      // 5.3..2
      if (h[j] < h[i])
      {
        int k = i + h[j];
        if (r[k] == j && h[k] != h[j]) // exclude 211
          res++;
      }
    }
  }

  for (int i = 0; i < n; i++)
  {
    int j = l[i];
    if (j < 0)
      continue;

    // 5.2..3
    if (l[j] >= 0 && h[l[j]] == h[i] + h[j])
      res++;

    // 3.2..5
    int k = i + h[j];
    if (r[j] != i && k < n && h[k] == h[i] + h[j]) // exclude 112
      res++;
  }

  // k.2.i5.3..j
  res += calcTriangle(h);
  // exclude 121
  for (int i = 0; i < n; i++)
    if (h[i] % 2 == 0)
    {
      int u = i - h[i] / 2, v = i + h[i] / 2;
      if (u >= 0 && h[u] == h[i] / 2 && v < n && h[v] == h[i] / 2)
        res--;
    }

  return res;
}

vector<int> construct_range(int M, int K) {
  // vector<int> PATTERN = {2, 3, 4, 1, 2, 1, 3};
  vector<int> PATTERN = {1, 2, 1, 1, 3, 6, 5, 4};
  vector<int> ans;
  while (size(ans) < M)
  {
    for (int x : PATTERN)
      ans.push_back(x);
  }
  ans.resize(M);
  return ans;
}

• Subtask 0: 0 / 0
• Subtask 1: 8 / 8
• Subtask 2: 6 / 6
• Subtask 3: 10 / 10
• Subtask 4: 11 / 11
• Subtask 5: 16 / 16
• Subtask 6: 19 / 19
• Subtask 7: 4.8333 / 5
• Subtask 8: 2.1725 / 5
• Subtask 9: 0.8745 / 5
• Subtask 10: 0.375 / 5
• Subtask 11: 0.4375 / 5
• Subtask 12: 0.1458 / 5