How should I practice First Duplicate Value?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Microsoft onsite interview problems in FastPrep.

Is First Duplicate Value associated with Microsoft?

FastPrep tags this as a Microsoft onsite interview coding practice problem when the problem catalog has that company and stage context.

First Duplicate Value

Microsoft● EasyFULLTIMEONSITE INTERVIEW

Learn

Problem statement

Scan values from left to right. Return the first value whose current occurrence has appeared earlier in the array. Equivalently, choose the duplicate whose second occurrence has the smallest index.

Return -1 when no value occurs twice.

Function

firstDuplicate(values: int[]) → int

Examples

Example 1

values = [2,1,3,5,3,2]return = 3

The second occurrence of 3 appears before the second occurrence of 2.

Example 2

values = [1,2,3,4]return = -1

Every value is unique.

Constraints

0 <= values.length <= 200000.
0 <= values[i] <= 1000000000.