Leetcode | 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".

这里用了一个vector来模拟栈。方便正序输出。

class Solution {
public:
    string simplifyPath(string path) {
        if (path.empty()) return "/";
        path.push_back('/');
        int start = -1, end;
        vector<string> st;
        while ((end = path.find('/', start + 1)) != string::npos) {
            string tmp = "";
            if (end - start - 1) {
                tmp = path.substr(start + 1, end - start - 1);
            }
            if (tmp == ".." && !st.empty()) st.pop_back();
            if (!tmp.empty() && tmp != "." && tmp != "..") st.push_back(tmp);
            start = end;
        }
        stringstream ans;
        for (int i = 0; i < st.size(); i++) {
            ans << '/' << st[i];
        }
        if (!ans.str().empty()) return ans.str();
        return "/";
    }
};