Which description correctly states how the palindrome check initializes and progresses its indices?

• A. Left starts at 0 and right at length(s) - 1; left is incremented and right is decremented each iteration.
• B. Left starts at 0; Right starts at length(s) - 1; Both indices are incremented.
• C. Left starts at length(s) - 1; Right starts at 0.
• D. Left and right start at 0 and remain fixed.

Answer: (A)

The check uses two pointers that start at opposite ends of the string and move toward the center. One pointer begins at the first character (index 0) and the other at the last character (index length(s) - 1). In each step you compare the characters at these positions; if they match, you advance the left pointer and retreat the right pointer. You continue until the two pointers meet or cross. This approach directly tests symmetry from both ends inward, which is what defines a palindrome.

Starting with both pointers at the left and moving them forward would never compare the right-side characters. Starting with the left at the end and the right at the start would require moving in opposite directions to test symmetry, which is the reverse of the correct approach. Starting both at 0 and keeping them fixed wouldn’t compare different characters at all.