Merge Two Strings | Dataford Interview Questions

Your question is Merge Two Strings. Start with the requirements on the right.

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Problem

Tenable Vulnerability Management may combine two short alert labels into one display string. Given two strings, create an interleaved string by taking one character from the first string, then one from the second, repeating until both strings are exhausted.

Preserve the original character order within each input string. If one string is shorter, append the remaining characters from the other string after the alternating portion. The first character must always come from the first string when it is non-empty.

Formal Specification

Implement merge_strings(first, second):

Input: Two strings, first and second.
Output: A string containing all characters from both inputs exactly once, interleaved from left to right.
Empty strings are valid inputs.

Constraints

0 <= len(first), len(second) <= 10^5
Inputs contain printable ASCII characters
The output contains every input character exactly once
The output length is len(first) + len(second)

Function Signature

def merge_strings(first, second):