71. Simplify Path

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71. Simplify Path

Description

You are given an absolute path for a Unix-style file system, which always begins with a slash '/'. Your task is to transform this absolute path into its simplified canonical path .

The rules of a Unix-style file system are as follows:

  • A single period '.' represents the current directory.
  • A double period '..' represents the previous/parent directory.
  • Multiple consecutive slashes such as '//' and '///' are treated as a single slash '/'.
  • Any sequence of periods that does not match the rules above should be treated as a valid directory or file name. For example, '...' and '....' are valid directory or file names.

The simplified canonical path should follow these rules:

  • The path must start with a single slash '/'.
  • Directories within the path must be separated by exactly one slash '/'.
  • The path must not end with a slash '/', unless it is the root directory.
  • The path must not have any single or double periods ('.' and '..') used to denote current or parent directories.

Return the simplified canonical path .

Example 1:

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Input: path = "/home/"

Output: "/home"

Explanation:

The trailing slash should be removed.

Example 2:

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Input: path = "/home//foo/"

Output: "/home/foo"

Explanation:

Multiple consecutive slashes are replaced by a single one.

Example 3:

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Input: path = "/home/user/Documents/../Pictures"

Output: "/home/user/Pictures"

Explanation:

A double period ".." refers to the directory up a level (the parent directory).

Example 4:

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Input: path = "/../"

Output: "/"

Explanation:

Going one level up from the root directory is not possible.

Example 5:

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Input: path = "/.../a/../b/c/../d/./"

Output: "/.../b/d"

Explanation:

"..." is a valid name for a directory in this problem.

Constraints:

  • 1 <= path.length <= 3000
  • path consists of English letters, digits, period '.', slash '/' or '_'.
  • path is a valid absolute Unix path.

Hints/Notes

Solution

Language: C++

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class Solution {
public:
    string simplifyPath(string path) {
        stack<string> dirs;
        istringstream ss(path);
        string s;
        while (getline(ss, s, '/')) {
            if (s.empty() || s == ".") {
                continue;
            }
            if (s != "..") {
                dirs.push(s);
            } else if (!dirs.empty()) {
                dirs.pop();
            }
        }
        string res;
        while (!dirs.empty()) {
            res = '/' + dirs.top() + res;
            dirs.pop();
        }
        return res.empty() ? "/" : res;

    }
};