Practice/Meta/Leetcode 71. Simplify Path

Leetcode 71. Simplify Path

CodingMust

Problem

You are given a string representing an absolute path in a Unix-style file system. Your task is to convert this path into its simplified canonical form.

In a Unix-style file system:

• A single period . refers to the current directory
• A double period .. refers to the parent directory (one level up)
• Multiple consecutive slashes // are treated as a single slash /
• The path always starts with a single slash / (indicating the root)

The canonical path must follow these rules:

• It must start with a single slash /
• Directories are separated by exactly one slash /
• It must not end with a trailing slash / (unless the path is just the root directory)
• It must not contain any . or .. references
• Going up from the root directory (using ..) keeps you at root

Requirements

1. Return the simplified canonical version of the given absolute path
2. Handle all directory navigation symbols correctly (. and ..)
3. Collapse multiple consecutive slashes into a single slash
4. Remove trailing slashes except when the result is the root directory
5. Ensure that attempts to navigate above the root directory are ignored

Constraints

• 1 ≤ path.length ≤ 3000
• path consists of English letters, digits, period ., slash /, or underscore _
• path is a valid absolute Unix path (starts with /)
• Expected time complexity: O(n) where n is the length of the path
• Expected space complexity: O(n) for storing the result

Examples

Example 1:

Input: path = "/home/user/../documents" Output: "/home/documents" Explanation: The ".." moves up one directory from "user" to "home", then we continue to "documents".

Example 2:

Input: path = "/a/./b/../../c/" Output: "/c" Explanation: Step by step: start at root → a → stay at a (.) → b → back to a (..) → back to root (..) → c. The trailing slash is removed.

Example 3:

Input: path = "/../" Output: "/" Explanation: Attempting to go above the root directory keeps us at root. The result is just "/".

Example 4:

Input: path = "/home//documents///file.txt" Output: "/home/documents/file.txt" Explanation: Multiple consecutive slashes are collapsed into a single slash.