How should I practice Most Frequent Valid Substring?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Visa online assessment problems in FastPrep.

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Most Frequent Valid Substring

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Problem statement

You are given a string s and integers minLength, maxLength, and maxUnique.

A substring is valid when:

its length is between minLength and maxLength, inclusive, and
it contains at most maxUnique distinct characters.

Return the greatest number of occurrences of any one valid substring in s. Occurrences may overlap. Return 0 if no substring is valid.

Function

mostFrequentValidSubstring(s: String, minLength: int, maxLength: int, maxUnique: int) → int

Examples

Example 1

s = "aababcaab"minLength = 2maxLength = 3maxUnique = 2return = 3

The valid substring ab occurs three times, starting at indices 1, 3, and 7.

Example 2

s = "aaaa"minLength = 1maxLength = 3maxUnique = 1return = 4

The length-one substring a is valid and occurs four times.

Constraints

1 <= s.length <= 10⁴
1 <= minLength <= maxLength <= s.length
1 <= maxUnique <= 128
s contains printable ASCII characters.