Implementation lab in Sorting and Divide-and-Conquer

Mission

Merge two sorted arrays in stable order.

Learning outcome: Implement stable merging

Correctness contract

Invariant: A selection prefix is final; a merge emits the smallest remaining head.

Required technique: Merge with two forward indexes, taking from the left sequence on equality.

Complexity target: time O(n+m); space O(n+m).

Input and output

Input: n, then n sorted integers, then m, then m sorted integers. Whitespace may be spaces or line breaks.

Output: Print the requested sequence on one line with single spaces and no trailing space. Return it as a String; Main.java prints it without adding other text.

Assumptions:

• Both input sequences are sorted in nondecreasing order.

Before you code

1. Restate the input and output contract, then predict the visible example without running code.
2. Implement the core state transition: Merge with two forward indexes, taking from the left sequence on equality.
3. Trace the smallest boundary case, verify exact formatting, and justify the authored time and auxiliary-space bounds.

Implement Practice.solve(Scanner sc). Keep every provided filename and public class name unchanged.

Sample input

3 1 4 7 3 2 3 9

Sample output

1 2 3 4 7 9

Why the sample works: Visible walkthrough for the ordinary non-trivial path. Two indexes repeatedly select the smaller front value, choosing the first array on equality. Input `3 1 4 7 3 2 3 9` therefore produces `1 2 3 4 7 9`.

Progressive hints

Try the trace and first milestone before opening a hint. Open them in order.

Hint 1 — Contract: identify what each parsed variable represents and write the invariant beside the loop or recursive method.

Hint 2 — Next step: When values tie, consume the left input first; this keeps the merge stable.

Hint 3 — Verification: compare the structure state before and after one operation, then test the smallest valid input and a duplicate or unreachable case when allowed.