剑指 Offer II 014. 字符串中的变位词

 func checkInclusion(_ s1: String, _ s2: String) -> Bool {
 let m = s1.count
        let n = s2.count
        if m > n {
            return false
        }
        let tempValue :Character = "a"
        
        var array1 = Array<Int>(repeating: 0, count: 26)
        var array2 = Array<Int>(repeating: 0, count: 26)
        let temp1 = Array(s1)
        let temp2 = Array(s2)

        for i in 0..<temp1.count {
            array1[Int((temp1[i].asciiValue ?? 0) - (tempValue.asciiValue ?? 0))] += 1
            array2[Int((temp2[i].asciiValue ?? 0) - (tempValue.asciiValue ?? 0))] += 1

        }
    
        if array1 == array2 {
            
            return true
        }
 

        for i in m..<n {
                                
            array2[Int((temp2[i].asciiValue ?? 0) - (tempValue.asciiValue ?? 0))] += 1
            array2[Int((temp2[i - m].asciiValue ?? 0) - (tempValue.asciiValue ?? 0))] -= 1
            if array1 == array2 {
            
                return true
            }
        }
        
        
        return false
    }