leetcode 71. Simplify Path

 1 string simplifyPath(string path) 
 2     {
 3         vector<string> dirs;  
 4         int start = 0, end = 0;
 5         
 6         while (end < path.size())
 7         {
 8             while (start < path.size() && path[start] == ‘/‘)
 9                 start++;
10             end = start;
11             while (end < path.size() && path[end] != ‘/‘)
12                 end++;
13             string str = path.substr(start, end - start);
14             if (str == "..")
15             {    
16                 if (!dirs.empty())
17                     dirs.pop_back();
18             }
19             else if (str != "." && str != "")
20             {
21                 dirs.push_back(str);
22             }
23             start = end;
24         }
25         
26         path = "";
27         for (int i = 0; i < dirs.size(); i++)
28             path += "/" + dirs[i];
29         
30         return (path == "") ? "/" : path;
31     }