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Replace the Substring for Balanced String

You are given a string s of length n containing only four kinds of characters: 'Q', 'W', 'E', and 'R'.

You are given a string s of length n containing only four kinds of characters: 'Q', 'W', 'E', and 'R'.

A string is said to be balanced if each of its characters appears n / 4 times where n is the length of the string.

Return the minimum length of the substring that can be replaced with any other string of the same length to make s balanced. If s is already balanced, return 0.

Replace the Substring for Balanced String diagram

Example 1

Input: s = "QWER"

Output: 0

Explanation: s is already balanced.

Example 2

Input: s = "QQWE"

Output: 1

Explanation: We need to replace a 'Q' to 'R', so that "RQWE" (or "QRWE") is balanced.

Example 3

Input: s = "QQQW"

Output: 2

Explanation: We can replace the first "QQ" to "ER".

Constraints

  • n == s.length
  • 4 <= n <= 10^5
  • n is a multiple of 4.
  • s contains only 'Q', 'W', 'E', and 'R'.

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