LeetCode | 71. Simplify Path

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".

思路：用双向队列deque来实现栈和按位访问的功能。遇到”.”就跳过，遇到”..”，若栈顶不为空，就弹出一个元素。遇到”//”这样的多重斜杠就跳过。最后按照格式输出即可。

//6 ms AC
class Solution {
public:
    string simplifyPath(string path)
    {
        string res = "", tmp = "";
        deque<string> d;
        int len = path.length(), it = 0;

        while(it < len)
        {
            if(path[it] == '/')
            {
                it++;
                tmp.clear();
                while(path[it]!='/' && it<len)
                    tmp += path[it++];
                if(tmp == ".")
                    continue;
                else if(tmp == "..")    //返回上一级
                {
                    if(d.empty())
                        continue;
                    else
                        d.pop_back();
                }
                else if(tmp != "")
                    d.push_back(tmp);
            }
        }

        res += '/';
        deque<string>::iterator i = d.begin();
        while(i != d.end())
        {
            res += *i;
            res += '/';
            i++;
        }

        if(res.length() != 1)
            res = res.substr(0,res.length()-1);

        return res;
    }
};