[Leetcode] Simplify Path

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

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

用栈实现即可，注意一些特殊情况的判断。

class Solution {
public:
    string simplifyPath(string path) {
        stack<string> s;
        string str;
        int a, b;
        bool flag = true;
        for (int i = 0; i < path.length(); ++i) {
            if (path[i] == '/') {
              path[i] = ' ';
            }
        }
        istringstream sin(path);
        while (sin >> str) {
            if (str == ".." && !s.empty()) {
                s.pop();
            } else if (str == "." || str == ".." && s.empty()) {
                
            } else {
                s.push(str);
            }
        }
        string res = "";
        if (s.empty()) {
            return "/";
        }
        while (!s.empty()) {
            res = "/" + s.top() + res;
            s.pop();
        }
        return res;
    }
};