Encrypt String With Shift | Dataford Interview Questions

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Problem

Hitachi Vantara tools may need lightweight text transformations for demonstrations or test fixtures. Implement a Caesar-shift function that encrypts an ASCII string by moving each alphabetic character forward by a given integer shift.

Requirements

Shift lowercase letters within a through z and uppercase letters within A through Z.
Wrap around when a shift passes z or Z.
Support positive, zero, and negative shift values. A negative shift moves characters backward.
Preserve the case of every letter.
Leave digits, whitespace, punctuation, and other non-ASCII characters unchanged.

Formal Specification

Input: text, a string, and shift, an integer.
Output: A new string containing the transformed characters.
The function must not modify the original string.
This is a reversible Caesar transformation, not production-grade encryption.

Constraints

0 <= len(text) <= 10^5
-10^9 <= shift <= 10^9
Only ASCII letters are shifted
Digits, whitespace, punctuation, and other Unicode characters remain unchanged

Function Signature

def encrypt_string(text, shift):