Find all Symmetric pairs in an array
Detailed guide and Python implementation for the 'Find all Symmetric pairs in an array' problem.
Problem Statement
Write a function symmetric_pairs(arr) that takes a list of pairs (list of 2-element lists) and returns all symmetric pairs. A pair [a, b] is symmetric with another pair [b, a] if both exist in the array. Return the result as a sorted list of pairs where the first element of the pair is smaller. Each symmetric pair should appear only once.
- •1 <= len(arr) <= 10^4
- •Each element is a list of 2 integers
- •-10^6 <= arr[i][j] <= 10^6
Examples
arr = [[1, 2], [2, 1], [3, 4], [4, 3], [5, 6]]
[[1, 2], [3, 4]]
[1,2] and [2,1] are symmetric. [3,4] and [4,3] are symmetric. [5,6] has no symmetric pair.
arr = [[1, 2], [3, 4]]
[]
No pair has its reverse in the array.
arr = [[10, 20], [20, 10]]
[[10, 20]]
[10,20] and [20,10] form a symmetric pair.
Need a Hint?
Edge Cases to Watch
- Empty input structures
- Single element inputs
- Large numerical bounds
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