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  1. #include <algorithm>
  2. #include <exception>
  3. #include <iostream>
  4. #include <list>
  5.  
  6. int detach(std::list<int>& l)
  7. {
  8.     if (l.size() < 2) {
  9.         throw std::runtime_error("too short list");
  10.     }
  11.     auto it = std::is_sorted_until(l.begin(), l.end());
  12.     if (it == l.end()) {
  13.         throw std::runtime_error("already sorted list");
  14.     }
  15.     if (!std::is_sorted(it, l.end())) {
  16.         throw std::runtime_error("not 'partially' sorted list");
  17.     }
  18.     if (std::prev(it) == l.begin() || *it < *std::prev(it, 2)) {
  19.         auto res = *it;
  20.         l.erase(it);
  21.         return res;
  22.     } else {
  23.         auto res = *std::prev(it);
  24.         l.erase(std::prev(it));
  25.         return res;
  26.     }
  27. }
  28.  
  29. void test(std::list<int> l)
  30. {
  31.     try {
  32.         std::cout << detach(l) << std::endl;
  33.         if (!std::is_sorted(l.begin(), l.end())) {
  34.              std::cout << "result not sorted\n";
  35.         }
  36.     } catch (const std::exception& e) {
  37.         std::cout << e.what() << std::endl;
  38.     }	
  39.  
  40. }
  41.  
  42. int main() 
  43. {
  44.     test({1}); // too short list
  45.     test({1, 2, 3}); // already sorted list
  46.     test({1, 3, 2, 0}); // not partially sorted list
  47.  
  48.     test({3, 1}); // 3 or 1 (currently 1)
  49.     test({3, 1, 5}); // 1
  50.     test({1, 4, 2, 10}); // 4 or 2 (currently 4)
  51.     test({28, 144, 44, 52, 60}); // 144
  52.     test({60, 68, 76, 84, 65, 100}); // 65
  53. }
  54.  
Success #stdin #stdout 0s 4364KB
comments (?)
stdin 
Standard input is empty
stdout 
too short list
already sorted list
not 'partially' sorted list
1
1
4
144
65
https://ideone.com/w0ujcQ
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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