【字符串】917. 仅仅反转字母

 1 class Solution {
 2 public:
 3     string reverseOnlyLetters(string S) 
 4     {
 5         int begin = 0;
 6         int end = S.size()-1;
 7 
 8         while(begin <= end)
 9         {
10             if(!isalpha(S[begin]))
11             {
12                 begin++;
13             }
14             else if(!isalpha(S[end]))
15             {
16                 end--;
17             }
18             else if(isalpha(S[begin]) && isalpha(S[end]))
19             {
20                 swap(S[begin], S[end]);
21                 begin++;
22                 end--;
23             }
24         }  
25 
26         return S;      
27     }
28 };