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2947. Count Beautiful Substrings I

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	`1`	`+class Solution {`
	`2`	`+`
	`3`	`+ // Solution by Sergey Leschev`
	`4`	`+ // 2947. Count Beautiful Substrings I`
	`5`	`+`
	`6`	`+ // Time complexity: O(n+k)`
	`7`	`+ // Space complexity: O(n)`
	`8`	`+`
	`9`	`+ func beautifulSubstrings(_ s: String, _ k: Int) -> Int {`
	`10`	`+ var grps = [Int: [Int]]()`
	`11`	`+ grps[0] = [0]`
	`12`	`+`
	`13`	`+ let vowels: Set<Character> = Set("aeiou")`
	`14`	`+ var presum = 0`
	`15`	`+`
	`16`	`+ for (i, char) in s.enumerated() {`
	`17`	`+ if vowels.contains(char) {`
	`18`	`+ presum += 1`
	`19`	`+ } else {`
	`20`	`+ presum -= 1`
	`21`	`+ }`
	`22`	`+ grps[presum, default: []].append(i + 1)`
	`23`	`+ }`
	`24`	`+`
	`25`	`+ var x = 1`
	`26`	`+ while x <= k && x * x % k != 0 {`
	`27`	`+ x += 1`
	`28`	`+ }`
	`29`	`+ x *= 2`
	`30`	`+`
	`31`	`+ var ans: Int64 = 0`
	`32`	`+ for (_, grp) in grps {`
	`33`	`+ var mod = [Int](repeating: 0, count: x)`
	`34`	`+ for i in grp {`
	`35`	`+ ans += Int64(mod[i % x])`
	`36`	`+ mod[i % x] += 1`
	`37`	`+ }`
	`38`	`+ }`
	`39`	`+ return Int(ans)`
	`40`	`+ }`
	`41`	`+}`

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