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  1. # divide et impera
  2. def __summa(lo, hi, arr):
  3.  
  4.     if lo == hi:
  5.         return arr[lo]
  6.     else:
  7.         m = (lo + hi) >> 1
  8.         a = __summa(lo, m, arr)
  9.         b = __summa(m + 1, hi, arr)
  10.         s = a + b
  11.         return s
  12.  
  13. # loop standard
  14. def _summa(arr):
  15.     s = 0
  16.     for i in range(0, len(arr)):
  17.         s = s + arr[i]
  18.     return s
  19.  
  20. # head and tail list
  21. def summa(arr):
  22.     if arr == []:
  23.        return 0
  24.     else:
  25.        return arr[0] + summa(arr[1:])
  26. def main():
  27.     arr = [1,2,3,4,5,6,7,8,9,10]
  28.     n = len(arr)
  29.     s = __summa(0, len(arr) - 1, arr)
  30.     print(s)
  31.     print(s == summa(arr) == _summa(arr) == n * (n  + 1 )//2)
  32. main()
Success #stdin #stdout 0.02s 9136KB
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https://ideone.com/bhVJRT
Sum list with head and tail
language:
Python 3 (python  3.9.5)
created:
3 years ago
visibility:
secret

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