How should I practice Get Min Cost Data 🍊?

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Get Min Cost Data 🍊

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Problem statement

You are given a string data containing lowercase English letters and question marks. Replace every ? with a lowercase English letter.

The cost of a position is the number of earlier positions containing the same letter. Equivalently, if a letter appears f times in the completed string, it contributes f * (f - 1) / 2 to the total cost.

Return a completed string with the minimum possible total cost. If several completed strings have that minimum cost, return the lexicographically smallest one.

Function

getMinCostData(data: String) → String

Examples

Example 1

data = "aaaa?aaaa"return = "aaaabaaaa"

Replacing ? with b creates no additional equal-letter pair and is the lexicographically smallest minimum-cost choice.

Example 2

data = "??????"return = "abcdef"

Using six distinct letters gives total cost 0. Sorting the chosen letters produces the smallest such string, abcdef.

Example 3

data = "abcd?"return = "abcde"

Choosing a through d would repeat an existing letter and add cost. The smallest unused letter is e, so abcde has minimum cost 0.

Constraints

1 <= data.length <= 10^5
data contains lowercase English letters and ? only.
data contains at least one ?.