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2949. Count Beautiful Substrings II

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	`1`	`+class Solution {`
	`2`	`+`
	`3`	`+ // Solution by Sergey Leschev`
	`4`	`+ // 2949. Count Beautiful Substrings II`
	`5`	`+`
	`6`	`+ // Time Complexity: O(n + k)`
	`7`	`+ // Space Complexity: O(n + k)`
	`8`	`+`
	`9`	`+ func beautifulSubstrings(_ s: String, _ k: Int) -> Int {`
	`10`	`+ let n = s.count`
	`11`	`+ var v = 0`
	`12`	`+ var l = 1`
	`13`	`+ while l * l % (k * 4) != 0 {`
	`14`	`+ l += 1`
	`15`	`+ }`
	`16`	`+`
	`17`	`+ let vowels: Set<Character> = ["a", "e", "i", "o", "u"]`
	`18`	`+ var seen = Array(repeating: [Int: Int](), count: l)`
	`19`	`+ seen[l - 1][0] = 1`
	`20`	`+ var res: Int64 = 0`
	`21`	`+`
	`22`	`+ for (i, char) in s.enumerated() {`
	`23`	`+ v += vowels.contains(char) ? 1 : -1`
	`24`	`+ res += Int64(seen[i % l][v] ?? 0)`
	`25`	`+ seen[i % l][v, default: 0] += 1`
	`26`	`+ }`
	`27`	`+`
	`28`	`+ return Int(res)`
	`29`	`+ }`
	`30`	`+}`

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