Surface the Repeat Offenders

Advanced

A fraud check flags values that appear more than once in a transaction stream. Report each repeated value a single time, in the order it first becomes a repeat.

Implement `solve(List<Integer> nums)` to return the values that appear more than once, each listed once, in the order each first becomes a duplicate.

Examples

Input[4, 3, 2, 7, 3, 2, 2]

Output[3, 2]

Input[1, 1, 1]

Output[1]

Hints

Track seen and already-added values in two Sets while scanning.

Anonymous Apex

List<Integer> solve(List<Integer> nums) {
    // return values that repeat, in first-duplicate order
    return null;
}

Your code runs in a secure sandbox against multiple hidden test cases. The problem is solved only when every test passes. Each run is isolated and any data changes are rolled back automatically.