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:
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]
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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
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