LeetCode-Easy部分中标签为String 434. Number of Segments in a String。

原题

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

Input: "          "
Output: 0

Input: "     a"
Output: 1

Input: "     a        "
Output: 1

Input: "     a                b    "
Output: 2

代码分析

求字符串的片段字符串个数。首要看 segment 的定义：

a segment is defined to be a contiguous sequence of non-space characters.

意味着我们可以写出以下2个API来判断每个字符串的第一个片段，然后递归求所有字符片段的个数。

        //字符串的第一个片段的首字符，找到有效字符开始
        private bool isValidBegin(char curchar)
        {
            if (curchar != ' ')
                return true;
            return false;
        }


        //判断字符片段的结束
        private bool isValidEnd(char curchar, char afterchar)
        {
            if (curchar != ' ' && afterchar == ' ')
                return true;
            return false;
        }

代码实现

递归版：

       public int CountSegments(string s)
        {
            if (string.IsNullOrEmpty(s)) 
                return 0;
            int i = 0;
            while (i < s.Length && !isValidBegin(s[i])) 
                i++;
            if (i == s.Length) //没有有效字符，如"         "
                return 0;
            if (i == s.Length - 1)  //只有一个有效字符，如 "         a"
                return 1;
            while (i < s.Length - 1 && !isValidEnd(s[i], s[i + 1]))
                i++;
            if (i == s.Length - 1)
                return 1; //只有1个有效字符，如"         a              "

            return 1+ CountSegments(s.Substring(i + 1));
        }