LeetCode 784 Letter Case Permutation - Implementation

Backtrack with branch on letters.

function letterCasePermutation(s): result = [] def backtrack(index, current): if index == len(s): result.append(current) return char = s[index] if char.isalpha(): backtrack(index + 1, current + char.lower()) backtrack(index + 1, current + char.upper()) else: backtrack(index + 1, current + char) backtrack(0, "") return result

$O(n \cdot 2^k)$ where $k$ is letter count.