0071.Simplify Path

Link: 71. Simplify Path - Medium

Question

Restate the problem

Given a string, Unix-style absolute path, return simplified canonical path.

Method

Key idea

Split path by /, iterate each directory token, use a stack to simulate directory navigation, then rebuild the path.

Complexity

• Time Complexity: O(n)
• Space Complexity: O(n)

Edge case

• "/" return "/"
• "/../" → "/" (can’t go above root)
• Tokens like "..." are not special → keep them (folder name)

Code

class Solution:
    def simplifyPath(self, path: str) -> str:
        stack = []
        for token in path.split("/"):
            if token in ("", "."):
                continue
                
            if token == "..":
                if stack:
                    stack.pop()
                    continue
            else:
                stack.append(token)
        
        return "/" + "/".join(stack)