Second Last Index Method | Dataford Interview Questions

NCR Voyix checkout and transaction text may contain repeated marker characters such as |, :, or /. Implement get_second_last_index_of(s, ch) to return the zero-based index of the second-last occurrence of ch in s.

The method must scan the string once from left to right, use O(1) additional space, and must not use built-in operations that directly locate or count occurrences, such as count, rfind, rindex, find, slicing with reversal, or regular expressions. If ch occurs fewer than two times, return -1.

Formal Specification

Input s: a Python string, possibly empty.
Input ch: a string containing exactly one character.
Output: an integer representing the zero-based index of the second-last occurrence of ch, or -1 when fewer than two occurrences exist.
Indices refer to Python string positions, including Unicode code points.

Constraints

0 <= len(s) <= 10^6
ch contains exactly one character
The algorithm must make one left-to-right pass
Use O(1) auxiliary space
Do not use count, find, rfind, rindex, reverse slicing, or regular expressions

Function Signature

def get_second_last_index_of(s, ch):

Your question is Second Last Index Method. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem

Formal Specification

Input s: a Python string, possibly empty.
Input ch: a string containing exactly one character.
Output: an integer representing the zero-based index of the second-last occurrence of ch, or -1 when fewer than two occurrences exist.
Indices refer to Python string positions, including Unicode code points.

Constraints

0 <= len(s) <= 10^6
ch contains exactly one character
The algorithm must make one left-to-right pass
Use O(1) auxiliary space
Do not use count, find, rfind, rindex, reverse slicing, or regular expressions

Function Signature

def get_second_last_index_of(s, ch):

Your question is Second Last Index Method. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.