Submission #1207639

#	Time	Username	Problem	Language	Result	Execution time	Memory
1207639		lopkus	Subway (info1cup19_subway)	C++20	100 / 100	5 ms	1728 KiB

subway

#include <bits/stdc++.h>

#define int long long

void solve() {
  int k;
  std::cin >> k;
  int h = 0;
  std::vector<std::pair<int,int>> ans;
  ans.push_back({1, 0});
  // h * (h - 1) / 2
  int node = 2;
  int last = 0;
  for(int i = 1; ; i++) {
    if(i * (i - 1) / 2 <= k) {
      last = i;
    }
    else {
      break;
    }
  }
  for(int i = 2; i <= last; i++) {
    ans.push_back({i, i - 1});
  }
  node = last + 1;
  k -= last * (last - 1) / 2;
  while(k > 0) {
    int lst = 0;
    for(int i = 1; ; i++) {
      if(i * (i - 1) / 2 <= k) {
        lst = i;
      }
      else {
        break;
      }
    }
    if(k <= last) {
      ans.push_back({node, k});
      break;
    }
    int prv = 1;
    for(int i = 1; i < lst; i++) {
      ans.push_back({node, prv});
      prv = node++;
    }
    k -= lst * (lst - 1) / 2;
  }
  std::cout << ans.size() << "\n";
  for(auto [x, y] : ans) {
    x -= 1;
    y -= 1;
    std::cout << x << " " << y << "\n";
  }
}


signed main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);

  int t = 1;
  //std::cin >> t;
  while (t--) {
      solve();
  }

  return 0;
}

• Subtask 1: 20 / 20
• Subtask 2: 30 / 30
• Subtask 3: 50 / 50