https://leetcode.com/problems/reverse-vowels-of-a-string/

Write a function that takes a string as input and reverse only the vowels of a string.

Example 1:

Given s = "hello", return "holle".

Example 2:

Given s = "leetcode", return "leotcede".

两个指针，查找交换字符。一开始忘记在SWAP之后，移动指针了，导致死循环。。。新学到一个string::npos indicates no matches。

1 #include 
      
        2 using namespace std; 3  4 class Solution { 5 public: 6 /* 7     bool isVowels(char chIn) 8     { 9         return ((toupper(chIn) == 'A' || toupper(chIn) == 'E' || toupper(chIn) == 'I' || toupper(chIn) == 'O' || toupper(chIn) == 'U'));10     }11 */12     13     string reverseVowels(string s) {14         int i = 0, j = s.length() - 1;15         string sVowels = "aeiouAEIOU";16 17         // Remember special case18         if (s == "" || s.length() == 0) return s;19         20         while (i < j)21         {22 //            while (!isVowels(s[i]) && (i < j)) i ++;23               while ((sVowels.find(s[i]) == string::npos) && (i < j)) i ++;24 //            while (!isVowels(s[j]) && (i < j)) j --;25               while ((sVowels.find(s[j]) == string::npos) && (i < j)) j --;  26                         27             if (i < j)28                 swap(s[i], s[j]);29             30             i ++;31             j --;32         }33 34         return s;35     }36 };37 38 int main ()39 {40     Solution testSolution;41     string result;42     43     result = testSolution.reverseVowels("hello");    44     cout << result << endl;45     46     char ch;47     cin >> ch;48     49     return 0;50 }
      

string::find - C++ Reference

http://www.cplusplus.com/reference/string/string/find/

string::npos - C++ Reference

http://www.cplusplus.com/reference/string/string/npos/