学步园

题目：

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

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

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".

解题：

用栈可以搞，一个点不用管，两个点pop，最后再逆序输出

代码：

class Solution {
public:
    string simplifyPath(string path) {
        stack<string> s;
        int pos = 0
        while(1) {
            string tmp = check(path, pos);
            if(tmp == "") break;
            if(tmp == ".") continue;
            if(tmp == "..") {
                if(!s.empty())
                    s.pop();
            }
            else
                s.push(tmp);
        }
        if(s.empty()) return "/";
        Print(s);
        return ans;
    }
private:
    string ans;
    string check(string path, int &pos) {
        while(path[pos] == '/') pos ++;
        string rec;
        int i;
        for(i = pos; i < path.size() && path[i] != '/'; i ++)
            rec += path[i];
        pos = i;
        return rec;
    }
    void Print(stack<string> s) {
        if(s.empty()) return ;
        string top = s.top();
        s.pop();
        Print(s);
        ans += '/';
        ans += top;
    }
};