434. Number of Segments in a String

/* 
Count the number of segments in a string, where a segment is defined to be a contiguous sequence of non-space characters.

Please note that the string does not contain any non-printable characters.

Example:

Input: "Hello, my name is John"
Output: 5
*/

/*
 Thinking: 
 1. 要考虑头尾空格的问题
 2. 要考虑没有空格的问题
 3. 要考虑中间多个空格的问题
 综合以上如果
 
 空格即为比较元素，字符串对于分割体来说，只存在两种元素，
 非空格，空格
 
 _----_----__-----
 符合这种0，1信号的问题，从0到1算作一个section，1降到0不计入，
 也可以理解为波峰波谷之间的关系抽象
 
*/

enum SecmentsStatus: String {
    case Space = " "
    case Other = "o"
    
    //切换状态，返回是否切换
    mutating func switchStatus(_ str: String) -> Bool {
        //把输入的子串转换对两种模式
        let covertStr = (str == SecmentsStatus.Space.rawValue) ? SecmentsStatus.Space : SecmentsStatus.Other
        
        //与当前状态相同，则不做改变
        if covertStr == self {  //相同直接返回，不做改变
            return false
        }
        
        //不同，则做切换
        switch self {
            case .Space:
                self = SecmentsStatus.Other
                return true
            
            case .Other:
                self = SecmentsStatus.Space
                return false
            
        }
    }
}

func secments(In str: String) -> Int {
    
    var beforeCharacter = SecmentsStatus.Space
    
    var count = 0
    for character in str.characters {
        //发生了切换则+1
        if beforeCharacter.switchStatus(String(character)) {
            count += 1
        }
    }
    
    return count
}

secments(In: "")
secments(In: "ab")
secments(In: "ab cd")
secments(In: "cd ef, defgh")
secments(In: "abc, def")