Added solution

Author: avidLearnerInProgress

reverse-only-letters.cpp

@@ -0,0 +1,33 @@
+class Solution {
+public:
+    
+    void swap(char &x, char &y){
+        auto t = x;
+        x = y;
+        y = t;
+    }
+    
+    string reverseOnlyLetters(string S) {
+        
+        if(S.size() == 0) return "";
+        
+        int i = 0, j = S.size() - 1;
+        
+        
+        while(i <= j){
+            
+            if(isalpha(S[i]) and isalpha(S[j]))
+                swap(S[i], S[j]);
+            
+            else if(!isalpha(S[i])){
+                i++; continue;
+            }
+            else if(!isalpha(S[j])){
+                j--; continue;
+            }
+        
+            i++; j--;
+        }
+        return S;
+    }
+};