How should I practice Remove Duplicate Characters?

Start by reading the full statement, solve the visible examples, then compare the pattern against related WhatNot phone screen problems in FastPrep.

Is Remove Duplicate Characters associated with WhatNot?

FastPrep tags this as a WhatNot phone screen coding practice problem when the problem catalog has that company and stage context.

Remove Duplicate Characters

WhatNot● EasyFULLTIMEPHONE SCREEN

Learn

Problem statement

Given a string s, remove repeated occurrences of each character so that every distinct character appears exactly once. Keep its first occurrence, preserving the order in which distinct characters first appear.

Duplicates may occur anywhere, not only next to each other. For example, abbaca becomes abc. Characters are not removed in pairs, and the output is not rearranged alphabetically.

Return the resulting string. An empty input produces an empty string.

Function

removeDuplicateCharacters(s: String) → String

Examples

Example 1

s = "banana"return = "ban"

The first appearances are b, a, n; later copies are removed.

Example 2

s = "cbacdcbc"return = "cbad"

Distinct characters first appear as c, b, a, d.

Example 3

s = ""return = ""

There are no characters to retain.

Constraints

0 <= s.length <= 10000.
s contains only lowercase English letters.