Application lab in Heaps and Priority Queues

Mission

Run highest-priority jobs first while preserving arrival order on ties.

Learning outcome: Apply priorities with stable tie-breaking

Correctness contract

Invariant: Every parent has priority over its children, and the root is the next item removed.

Required technique: Use a priority queue ordered by descending priority and ascending arrival index for ties.

Complexity target: time O(n log n); space O(n).

Input and output

Input: n followed by n name priority pairs in arrival order. 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:

• Job names contain no spaces; higher numeric priority runs first.

Before you code

1. Restate the input and output contract, then predict the visible example without running code.
2. Implement the core state transition: Use a priority queue ordered by descending priority and ascending arrival index for ties.
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

4 build 2 test 5 deploy 3 docs 2

Sample output

test deploy build docs

Why the sample works: Visible walkthrough for the ordinary non-trivial path. Higher numeric priority is removed first, while arrival index breaks equal-priority ties stably. Input `4 build 2 test 5 deploy 3 docs 2` therefore produces `test deploy build docs`.

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.