19.2.13 [LeetCode 71] Simplify Path

Given an absolute path for a file (Unix-style), simplify it. Or in other words, convert it to the canonical path.

In a UNIX-style file system, a period . refers to the current directory. Furthermore, a double period .. moves the directory up a level. For more information, see: Absolute path vs relative path in Linux/Unix

Note that the returned canonical path must always begin with a slash /, and there must be only a single slash / between two directory names. The last directory name (if it exists) must not end with a trailing /. Also, the canonical path must be the shortest string representing the absolute path.

 

Example 1:

Input: "/home/"
Output: "/home"
Explanation: Note that there is no trailing slash after the last directory name.

Example 2:

Input: "/../"
Output: "/"
Explanation: Going one level up from the root directory is a no-op, as the root level is the highest level you can go.

Example 3:

Input: "/home//foo/"
Output: "/home/foo"
Explanation: In the canonical path, multiple consecutive slashes are replaced by a single one.

Example 4:

Input: "/a/./b/../../c/"
Output: "/c"

Example 5:

Input: "/a/../../b/../c//.//"
Output: "/c"

Example 6:

Input: "/a//b////c/d//././/.."
Output: "/a/b/c"

题意

简化绝对路径，最后一个目录后不能有/

空路径写作"/"，如果要求访问根目录的上一级目录则自动简化为根目录自己，如例2

题解

class Solution {
public:
    string simplifyPath(string path) {
        string ans = "";
        int p = 0, l = path.length();
        while (p < l) {
            if (path[p] != '/') {
                string menu = "";
                while (p < l&&path[p] != '/')
                    menu += path[p++];
                if (menu == ".")
                    continue;
                else if (menu == "..") {
                    int idx = ans.rfind('/');
                    if (idx == string::npos)continue;
                    ans.erase(idx);
                }
                else
                    ans += "/" + menu;
            }
            p++;
        }
        if (ans.empty())return "/";
        return ans;
    }
};