Trace lab in Searching Ordered and Unordered Data

Mission

Report every inspected index and the first matching index, or -1 when the target is absent.

Learning outcome: Trace linear search evidence

Correctness contract

Invariant: The active interval contains every remaining position where the target could occur.

Required technique: Inspect values left to right, record every visited index, and stop immediately at the first match.

Complexity target: time O(n); space O(n) input and trace output.

Input and output

Input: n, then n integers, then one target integer. Whitespace may be spaces or line breaks.

Output: Print visited=<comma-separated indexes> result=<first index or -1>. Return it as a String; Main.java prints it without adding other text.

Assumptions:

• n is positive and all values and the target fit in signed 32-bit storage.

Before you code

1. Restate the input and output contract, then predict the visible example without running code.
2. Implement the core state transition: Inspect values left to right, record every visited index, and stop immediately at the first match.
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

5 4 8 1 8 3 8

Sample output

visited=0,1 result=1

Why the sample works: Visible walkthrough for the ordinary non-trivial path. Indexes are recorded from left to right until the first match, or through the last index when absent. Input `5 4 8 1 8 3 8` therefore produces `visited=0,1 result=1`.

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: Trace the smallest non-trivial input and write the structure state after the operation before coding the loop.

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.