﻿ Python: Find the indices of three numbers that sum to 0 in a list - w3resource

# 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]
```

Visual Presentation:

Sample Solution:

Python Code:

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

# Define a function named 'test' that takes a list of numbers as input
def test(nums):
inv = {n: i for i, n in enumerate(nums)}  # Create a dictionary to store the indices of numbers
# Note that later duplicates will override earlier entries

# Iterate through the indices and numbers in 'nums'
for i, n in enumerate(nums):
if inv[n] == i:
del inv[n]  # Remove the entry if it corresponds to the current index

# Check if there is a pair of indices (j, k) such that nums[j] + nums[k] + n = 0
if any((-m - n) in inv for m in nums[:i]):
# If a solution is found, get the indices (j, m) where nums[j] + m = -n
j, m = next((j, m) for j, m in enumerate(nums) if (-m - n) in inv)
# Get the index k for nums[k] = -m - n
k = inv[-m - n]
return sorted([i, j, k])  # Return the sorted list of indices

# Example 1
nums1 = [12, -7, 3, -89, 14, 4, -78, -1, 2, 7]
print("List of numbers:", nums1)
print("Indices of three numbers that sum to 0 in the said list:")
print(test(nums1))

# Example 2
nums2 = [1, 2, 3, 4, 5, 6, -7]
print("\nList of numbers:", nums2)
print("Indices of three numbers that sum to 0 in the said list:")
print(test(nums2))
``````

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:

Python Code Editor :

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