kmp 算法

 //https://blog.csdn.net/x__1998/article/details/79951598
    func gethexLong(_ str :String) -> [Int] {
        var next :[Int] = []
        
        for i  in 0..<str.count {

            let strItme = str.getStringRangeStr(0, i)
            print(strItme)
            if(i == 0){
                next.append(0)
            }else{
                let lastLength = next[i - 1]
                let lastStr = strItme.getStringChar(strItme.count - 1)//最后字符
                let firstStr = strItme.getStringChar(lastLength)//第一个字符
                if(lastStr == firstStr){
                   
                    next.append(lastLength + 1)
                }else{
                    let PfirstStr = strItme.getStringChar(0)//第一个字符
                    if(lastStr == PfirstStr){
                        next.append(1)
                    }else{
                        next.append(0)
                    }
                }
            }
        }
         print(next)
        return next
    }
    
    func kmp(_ mainStr :String ,_ pStr :String) -> Bool {
       
     let next = self.gethexLong(pStr)
        var j = 0
        var count = 0 //一共可以匹配的字符串个数
        for  i  in 0..<mainStr.count{
            
            let str  = mainStr.getStringChar(i)
            var strp = pStr.getStringChar(j)
            while str != strp{
                let lastCount = next[j-1]
                j = lastCount
                strp = pStr.getStringChar(j)
            }

                if j == pStr.count - 1{
                    count += 1
                    return true
                }else{
                    j += 1
                }
        }
        return false
    }