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Python Challenges: Find equilibrium index from a given array

Python Challenges - 1: Exercise-53 with Solution

Write a Python program to find equilibrium index from a given array. If there is no equilibrium index return 1.

Python: Find equilibrium index from a given array.
Ref: https://rosettacode.org/wiki/Equilibrium_index

Sample Solution:

Python Code:

def equilibrium(a):
  """https://bit.ly/33Spl45"""

  if len(a) == 0:
    return -1

  left_sum = 0

  for i in range(len(a) - 1):

    right_sum = 0
    middle_point = i + 1
    left_sum += a[i]

    for j in range(middle_point + 1, len(a)):
      right_sum += a[j]

    if left_sum == right_sum:
      return middle_point
  
  return -1

print(equilibrium([1,4,2,0,3,8,-4])) 
print(equilibrium([]))

Sample Output:

3
-1

Flowchart:

Python Flowchart: Find equilibrium index from a given array.

Python Code Editor:

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Python: Tips of the Day

Find current directory and file's directory:

To get the full path to the directory a Python file is contained in, write this in that file:

import os 
dir_path = os.path.dirname(os.path.realpath(__file__))

(Note that the incantation above won't work if you've already used os.chdir() to change your current working directory, since the value of the __file__ constant is relative to the current working directory and is not changed by an os.chdir() call.)

To get the current working directory use

import os
cwd = os.getcwd()

Documentation references for the modules, constants and functions used above:

  • The os and os.path modules.
  • The __file__ constant
  • os.path.realpath(path) (returns "the canonical path of the specified filename, eliminating any symbolic links encountered in the path")
  • os.path.dirname(path) (returns "the directory name of pathname path")
  • os.getcwd() (returns "a string representing the current working directory")
  • os.chdir(path) ("change the current working directory to path")

Ref: https://bit.ly/3fy0R6m