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  1. # Credits to Sergii Olshanetskyi
  2. # https://groups.google.com/g/google-code/c/nF6-5NEwLqE 
  3.  
  4. def get_boundaries(size):
  5.     return size - 1, (size + 2) * (size - 1) // 2
  6.  
  7. def swap(arr, s, e):
  8.     while s < e:
  9.         arr[s], arr[e] = arr[e], arr[s]
  10.         s += 1
  11.         e -= 1
  12.  
  13. number_of_cases = input()
  14.  
  15. for test_case_number in range(int(number_of_cases)):
  16.     input_params = input().split(" ")
  17.     N = int(input_params[0])
  18.     C = int(input_params[1])
  19.  
  20.     min_value, max_value = get_boundaries(N)
  21.  
  22.     if C < min_value or C > max_value:
  23.         print("Case #{}: {}".format(test_case_number + 1, "IMPOSSIBLE"))
  24.         continue
  25.  
  26.     current_C = C
  27.  
  28.     array = [-1] * N
  29.  
  30.     start_index = 0
  31.     last_index = len(array) - 1
  32.  
  33.     current_n = start_index + 1
  34.  
  35.     while start_index < last_index:
  36.         min_v, max_v = get_boundaries(N - current_n)
  37.  
  38.         if current_C - 1 < max_v:
  39.             array[start_index] = current_n
  40.             current_n += 1
  41.             start_index += 1
  42.             current_C -= 1
  43.             continue
  44.  
  45.         spooky_start = start_index
  46.         start = True
  47.  
  48.         while current_n <= N:
  49.             if start:
  50.                 array[start_index] = current_n
  51.                 start_index += 1
  52.             else:
  53.                 array[last_index] = current_n
  54.                 last_index -= 1
  55.  
  56.             current_n += 1
  57.             start = not start
  58.  
  59.         next_min_index = current_C - max_v
  60.  
  61.         swap(array, spooky_start, spooky_start + next_min_index - 1)
  62.  
  63.     result = ' '.join(str(i) for i in array)
  64.  
  65.     print("Case #{}: {}".format(test_case_number + 1, result))
Success #stdin #stdout 0.02s 9420KB
comments (?)
stdin
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5
4 6
2 1
7 12
7 2
2 1000
stdout
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Case #1: 1 3 4 2
Case #2: 1 2
Case #3: 1 2 3 5 7 6 4
Case #4: IMPOSSIBLE
Case #5: IMPOSSIBLE
https://ideone.com/lu7o2W
language:
Python 3 (python  3.12)
created:
4 years ago
visibility:
secret

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