In a common backtracking approach to generate

Solution

• Concept: Generating permutations using backtracking often involves swapping elements to explore different arrangements. After a recursive call returns, the swap needs to be undone (backtracked) to restore the array to its previous state for other branches of the recursion. • Code Analysis: o The for loop iterates from index to len(s)-1. o Inside the loop, s[index] is swapped with s[i] to place a different character at the current index position. o After the recursive call recurPermute(index + 1, s, ans), the swap needs to be reversed. • Explanation of Correct Answer (A): s[i], s[index] (for both lines) o The Pythonic way to swap two variables a and b is a, b = b, a. o To swap s[index] and s[i], the correct syntax is s[index], s[i] = s[i], s[index]. This line is used both for the initial swap before the recursive call and for the backtracking swap after the recursive call to restore the array.