71. Simplify Path

 

---

Given an absolute path for a file (Unix-style), simplify it. 

For example,
path = "/home/", => "/home"
path = "/a/./b/../../c/", => "/c"
path = "/a/../../b/../c//.//", => "/c"
path = "/a//b////c/d//././/..", => "/a/b/c"

In a UNIX-style file system, a period ('.') refers to the current directory, so it can be ignored in a simplified path. Additionally, a double period ("..") moves up a directory, so it cancels out whatever the last directory was. For more information, look here: https://en.wikipedia.org/wiki/Path_(computing)#Unix_style

Corner Cases:

• Did you consider the case where path = "/../"?
  In this case, you should return "/".
• Another corner case is the path might contain multiple slashes '/' together, such as "/home//foo/".
  In this case, you should ignore redundant slashes and return "/home/foo".

 

 

思路：

利用stack

如果是..   返回上一层目录----》弹栈

如果是. 或者空字符 啥也不操作

如果是字母：进入字母目录---》》 把字母压栈

 

class Solution {
public:
    string simplifyPath(string path) {
        string res,temp;
        stack<string> mystack ;
        stringstream  ss(path);
        while(getline(ss,temp,'/')){
            if(temp==".."){
                if(mystack.size()!=0)
                    mystack.pop();
            }
            else if(temp=="."||temp=="") 
                continue;
            else
                mystack.push(temp);
                
        }
         while (!mystack.empty()){
            res="/"+mystack.top()+res;
            mystack.pop();
            }
        
         return res.empty() ? "/" : res;

    }
   
};