Merge Sorted Array Prefix N

Background

In competitive programming, efficiently combining sorted lists is a common task. This problem asks you to merge two such lists and extract a specific prefix.

Problem Description

Given two arrays of strings, $A$ and $B$, each with its elements in alphabetical order and without duplicates. Return a new array containing the first $N$ elements obtained by merging the two arrays. The result array should also be in alphabetical order and without duplicates. Both $A$ and $B$ will have a length of $N$ or more.

The best "linear" solution makes a single pass over $A$ and $B$, taking advantage of their alphabetical order, copying elements directly to the new array.

Note: For this problem, $N$ is fixed at $3$.

Input Format

The input consists of a single line containing two string arrays, $A$ and $B$. Elements within each array are space-separated and enclosed in square brackets []. For example: ["a" "c" "z"] ["b" "f" "z"]. Please note that the actual input might exactly match the format shown in the examples, including potential missing brackets.

Output Format

The output should be a single line representing the new string array containing the first $N$ merged elements. Elements in the array are comma-separated, quoted, and enclosed in square brackets []. For example: `["a\