205. 同构字符串

func isIsomorphic(_ s: String, _ t: String) -> Bool {
        var map = Dictionary<Character,Character>()
        let length1 = s.count , length2 = t.count
        if length1 != length2 {
            return false
        }
        let array1 = Array(s) ,array2 = Array(t)
        for i in 0..<length1 {
            
            let key = array1[i]
            let temp = array2[i]
            //空的直接放进去
            if i == 0 {
                map[key] = temp
                
            }else {
                
                //如果在字典里面存在，在另外里面找值是否相等
                if let value = map[key] {
                    if value != temp {
                        return false
                    }
                    
                }
                //说明没有遇到过 判断是否可以放进去map
                else{
                    //不同字符不能映射到同一个字符上
                    if map.values.contains(temp){
                        return false
                    }else {
                        map[key] = temp
                    }
                    
                }
                
                
            }
            
            
           
        }
        
        return true

    
    }