How should I practice Longest Repeating Character Replacement?

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

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Problem · String

Longest Repeating Character Replacement

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Problem statement

Given a string s and an integer k, you may replace at most k characters with other uppercase English letters. Return the maximum length of a contiguous substring that can contain only one repeated character after these replacements.

For this exercise, assume the input contains only uppercase English letters. Return 0 for an empty string; replacements may be unused.

Function

characterReplacement(s: String, k: int) → int

Examples

Example 1

s = "ABAB"k = 2return = 4

Replace both B characters to obtain AAAA.

Example 2

s = "AABABBA"k = 1return = 4

The first four characters AABA can become AAAA with one replacement. Every length-five window needs at least two.

Example 3

s = ""k = 0return = 0

An empty string has length zero.

Constraints

0 <= s.length <= 10^5.
0 <= k <= s.length.
Every character is between A and Z.