844. 比较含退格的字符串

func backspaceCompare(_ s: String, _ t: String) -> Bool {

        let arrayS = Array(s) , arrayT = Array(t)
        var m = arrayS.count - 1 ,n =  arrayT.count - 1
        var tempM = 0 ,tempN = 0 ,valueM :Character = " " ,valueN :Character = " "
        while true  {
            
            if m >= 0 {
                valueM = arrayS[m]
            }else {
                valueM = " "
            }
            
            if n >= 0 {
                valueN = arrayT[n]
            }else {
                valueN = " "
            }

            if valueM == " " && valueN == " " {
            
                return true
            }
            
            if valueM == "#"{
                tempM += 1
                m -= 1
                
            }else if valueN == "#"{
                tempN += 1
                n -= 1

            }
            else if tempM != 0 {
                
                m -= 1
                tempM -= 1
                
            }else if tempN != 0 {
                
                n -= 1
                tempN -= 1
                
            }
            else if valueM == valueN {
                m -= 1
                n -= 1
            }
            else if valueM != valueN {
                
                return false
            
            }
            
        }

    
        
    }