Simplify Path

Problem Statement

Given an absolute Unix-style file system path, your task is to convert this path into a simplified version according to the Unix file system's conventions. In Unix systems, file paths begin with a '/' and use '/' to separate directory names. These paths may also contain identifiers like '.' and '..' which represent the current and parent directories, respectively. Furthermore, paths may contain redundant slashes or parts which need to be technologically aligned to a more readable and standardized format, called the canonical path. The simplified path must adhere to a specific set of rules, removing unnecessary or redundant characters and interpreting directory movements correctly.

Examples

Example 1

Input:

path = "/home/"

Output:

"/home"

Explanation:

The trailing slash should be removed.

Example 2

Input:

path = "/home//foo/"

Output:

"/home/foo"

Explanation:

Multiple consecutive slashes are replaced by a single one.

Example 3

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

Input:

path = "/../"

Output:

"/"

Explanation:

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

Example 5

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.

Approach and Intuition

For transforming the given path into its simplified canonical form, it's essential to decode the logic behind Unix file system paths:

1. Every sequential pair or group of slashes ('//', '///', etc.) should be treated as a single slash '/' in Unix paths, primarily meant for separating directories.
2. Symbols like '.' represent the current directory, whereas '..' implies moving up to the parent directory. These should be handled accordingly — neglecting the former, and effectively moving up a directory for the latter.
3. Periods not conforming to the above rules are part of valid filenames or directory names, such as '...'.
4. A valid simplified path should start with a '/' and not end with a '/' unless it's the root directory. This requirement also means that while reconstructing the path, adequate care must be taken to add slashes only when moving from one directory to another, without trailing the path end with unnecessary slashes.

Here's how we can logically approach the solution using the examples provided:

• Example 1 (/home/): Needs simplification by removing the trailing slash, as it's not the root.
• Example 2 (/home//foo/): Requires reduction of multiple slashes to a single one and removal of the trailing slash.
• Example 3 (/home/user/Documents/../Pictures): Interpreting '..' to move one directory up (from 'Documents' to 'user') ensures accurate directory traversal.
• Example 4 (/../): Shows that moving up from the root directory keeps you at the root, thus returning '/'.
• Example 5 (/.../a/../b/c/../d/./): Involves comprehensive parsing where '...' is a valid directory name, '..' moves up a directory, and '.' is the current directory and hence ignored.

Each step towards constructing the canonical path involves validating segments based on the specified rules, ensuring the final path is both compliant and devoid of any redundant or meaningless sequences. This methodological traversal and reconstruction provide clarity and adherence to Unix path conventions.

Solutions

class Solution {
public:
    string simplifyPath(string path) {
        vector<string> pathStack;
        stringstream ss(path);
        string component;
        while (getline(ss, component, '/')) {
            if (component == "..") {
                if (!pathStack.empty()) pathStack.pop_back();
            } else if (component != "." && !component.empty()) {
                pathStack.push_back(component);
            }
        }
        string result = "";
        for (auto dir : pathStack) result += "/" + dir;
        return result.empty() ? "/" : result;
    }
};