面试题33：简化目录路径

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

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

click to show corner cases.

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".

class Solution {
public:
    string simplifyPath(string path) {
        int n = path.size();
        stack<string> s;
        string dir;
        for (int i = 0; i < n; i++) {
            if (path[i] == '/') {
                if (!dir.empty()) {
                    s.push(dir);
                    dir.clear();
                }
            } else {
                dir.push_back(path[i]);
            }
        }
        if(!dir.empty()) s.push(dir);

        string res;
        int count = 0;
        while (!s.empty()) {
            string str = s.top();
            s.pop();
            if (str == ".") {
                continue;
            } else if (str == "..") {
                count++;
            } else {
                if (count > 0) {
                    count--;
                } else {
                    res = "/" + str + res;
                }
            }
        }
        if(res.length() == 0) return "/";
        return res;
    }
};