824. Goat Latin

1，题目要求
A sentence S is given, composed of words separated by spaces. Each word consists of lowercase and uppercase letters only.

We would like to convert the sentence to “Goat Latin” (a made-up language similar to Pig Latin.)

The rules of Goat Latin are as follows:

If a word begins with a vowel (a, e, i, o, or u), append “ma” to the end of the word.
For example, the word ‘apple’ becomes ‘applema’.

If a word begins with a consonant (i.e. not a vowel), remove the first letter and append it to the end, then add “ma”.
For example, the word “goat” becomes “oatgma”.

Add one letter ‘a’ to the end of each word per its word index in the sentence, starting with 1.
For example, the first word gets “a” added to the end, the second word gets “aa” added to the end and so on.
Return the final sentence representing the conversion from S to Goat Latin.

给定一个字符串，对于其中的每一个单词，如果该字母是以元音字母所开头的，那么就直接在该单词后面加上”ma”；如果不是，则将该单词的第一个字母已到单词最后，再加上”ma”。
最后，对于每一个单词，如果它是第k个单词，就在该单词最后加上k个’a’。

2，题目思路
就是基于特定条件的对字符串的便利操作。

3，程序源码

class Solution {
public:
    string toGoatLatin(string S) {
        string tmp = "", res = "", vol = "aeiouAEIOU";
        int count = 0;
        S = S + ' ';
        for(int i = 0;i<S.size();i++)
        {
            if(S[i] !=' ')
            {
                tmp += S[i];
                continue;
            }
            else        //find a word
            {
                count++;
                if(vol.find(tmp[0]) !=-1)   //begin with a vol
                    tmp += "ma";
                else
                {
                    char tt = tmp[0];
                    string ttmp = tmp.substr(1,tmp.size()-1);
                    tmp = ttmp + tt + "ma";
                }
                string aa(count,'a');
                res += tmp + aa + ' ';
            }
            tmp = "";
        }
        return res.substr(0,res.size()-1);
    }
};

注：

• s.find(char c)：找到s中对应的字符的index，如果没有，则返回-1。
• stirng s(int num, char c)：创建一个字符串，有num个c组成。
• s.substr(int index, int len)：获取一个字符串s的一个子串，该子串由索引index开始，长度为len。