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Python: Find the indices of three numbers that sum to 0 in a list

Python Programming Puzzles: Exercise-72 with Solution

Write a Python program to find the indices of three numbers that sum to 0 in a given list of numbers.

Input: [12, -7, 3, -89, 14, 4, -78, -1, 2, 7]
Output:
[1, 2, 5]

Input: [1, 2, 3, 4, 5, 6, -7]
Output:
[2, 3, 6]

Pictorial Presentation:

Python: Find the indices of three numbers that sum to 0 in a list.

Sample Solution:

Python Code:

#License: https://bit.ly/3oLErEI

def test(nums):
    inv = {n: i for i, n in enumerate(nums)}  # note that later duplicates will override earlier entries
    for i, n in enumerate(nums):
        if inv[n] == i:
            del inv[n]
        if any((-m - n) in inv for m in nums[:i]):  # found solution!
            j, m = next((j, m) for j, m in enumerate(nums) if (-m - n) in inv)
            k = inv[-m - n]
            return sorted([i, j, k])
 
nums = [12, -7, 3, -89, 14, 4, -78, -1, 2, 7]
 
print("List of numbers:",nums)
print("Indices of three numbers that sum to 0 in the said list:")
print(test(nums))
nums = [1, 2, 3, 4, 5, 6, -7]
print("\nList of numbers:",nums)
print("Indices of three numbers that sum to 0 in the said list:")
print(test(nums))

Sample Output:

List of numbers: [12, -7, 3, -89, 14, 4, -78, -1, 2, 7]
Indices of three numbers that sum to 0 in the said list:
[1, 2, 5]

List of numbers: [1, 2, 3, 4, 5, 6, -7]
Indices of three numbers that sum to 0 in the said list:
[2, 3, 6]

Flowchart:

Flowchart: Python - Find the indices of three numbers that sum to 0 in a list.

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Python Code Editor :

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Python: Tips of the Day

Decapitalizes the first letter of a string:

Example:

def tips_decapitalize(s, upper_rest=False):
  return s[:1].lower() + (s[1:].upper() if upper_rest else s[1:])
print(tips_decapitalize('PythonTips'))
print(tips_decapitalize('PythonTips', True)) 

Output:

pythonTips
pYTHONTIPS