Added reverse_vowels.cpp

Author: mandliya

leet_code_problems/reverse_vowels.cpp

@@ -0,0 +1,66 @@
+/*
+ * 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".
+ *
+ * Note:
+ * The vowels does not include the letter "y".
+ */
+
+#include <iostream>
+#include <algorithm>
+
+bool isVowel(char c)
+{
+    return (c == 'a' || c == 'e' ||
+            c == 'i' || c == 'o' ||
+            c == 'u' || c == 'A' ||
+            c == 'E' || c == 'I' ||
+            c == 'O' || c == 'U');
+}
+
+std::string reverseVowels(std::string s)
+{
+    if (s.length() == 0)
+    {
+        return s;
+    }
+    
+    unsigned int i = 0;
+    unsigned int j = s.length() - 1;
+    while (i < j)
+    {
+        while (i < j && !isVowel(s[i]))
+        {
+            i++;
+        }
+        
+        while (i < j && !isVowel(s[j]))
+        {
+            j--;
+        }
+        
+        if (i < j)
+        {
+            std::swap(s[i], s[j]);
+            ++i;
+            --j;
+        }
+    }
+    
+    return s;
+}
+    
+int main()
+{
+    std::string str;
+    std::cout << "Please enter input string: ";
+    std::cin >> str;
+    std::cout << "Expected output string: " << reverseVowels(str) << std::endl;
+
+    return 0;
+}