Binary Tree and String Reverse

EasyPython

Problem

A Citigroup transaction-monitoring component must locate a transaction amount in a sorted list and reverse a related reference string for downstream formatting. Implement both operations in one function.

Given a sorted list of integers amounts, an integer target, and a string reference, return a two-element list containing the index of target in amounts, or -1 if it is absent, followed by reference reversed character by character.

Use binary search for the lookup. If duplicate target values exist, returning any matching index is valid. Reverse the string without calling a built-in reverse helper.

Formal Specification

Input: amounts, a non-decreasing list of integers; target, an integer; and reference, a string.
Output: [index, reversed_reference], where index is a valid matching position or -1, and reversed_reference is the input string in reverse order.
The input string may contain spaces, punctuation, and mixed-case characters. Preserve every character exactly, changing only its position.

Constraints

0 <= len(amounts) <= 100,000
-10^9 <= amounts[i], target <= 10^9
amounts is sorted in non-decreasing order
0 <= len(reference) <= 100,000

Function Signature

def search_and_reverse(amounts, target, reference):

Use binary search for the lookup. If duplicate target values exist, returning any matching index is valid. Reverse the string without calling a built-in reverse helper.

Formal Specification

Input: amounts, a non-decreasing list of integers; target, an integer; and reference, a string.
Output: [index, reversed_reference], where index is a valid matching position or -1, and reversed_reference is the input string in reverse order.
The input string may contain spaces, punctuation, and mixed-case characters. Preserve every character exactly, changing only its position.