28. Implement strStr()

28. Implement strStr().swift

class Solution { // my code got timelimted error. this is new codes
    func strStr(_ haystack: String, _ needle: String) -> Int {
        guard !needle.isEmpty else { return 0 }
        guard haystack.count >= needle.count else { return -1 }
        
        let distance = haystack.count - needle.count
        for i in 0...distance {
            let start = haystack.index(haystack.startIndex, offsetBy: i)
            let end = haystack.index(haystack.startIndex, offsetBy: i+needle.count)
            
            if haystack[start..<end] == needle {
                return start.encodedOffset
            }
        }
        return -1
    }
}

the new code still gets time limited error