DSA · Stack · #163

Simplify Path

Module 45 · difficulty 3/5·⏱ 30:00starts on first keystroke

Given an absolute path `path` for a Unix-style file system, transform it into its **simplified canonical path**. In a Unix-style file system a single period `.` refers to the current directory, a double period `..` refers to the parent directory, and any sequence of multiple consecutive slashes (e.g. `//`) is treated as a single slash `/`. For this problem, any other sequence of periods (e.g. `...`) is treated as a valid directory/file name. The canonical path must: - Start with a single slash `/`. - Have exactly one slash between two directory names. - Not end with a trailing slash (unless it is the root). - Not contain any `.` or `..` components. Implement `simplifyPath(path)` returning the canonical path as a string.

Examples

path = "/home/" → "/home" — The trailing slash is removed.
path = "/../" → "/" — Going up from root stays at root.
path = "/home//foo/" → "/home/foo" — Multiple consecutive slashes collapse into one.

Constraints

· 1 <= path.length <= 3000
· path consists of English letters, digits, '.', '/', and '_'.
· path is a valid absolute Unix path, beginning with '/'.

Session phases

A · Clarify

B · Approach

C · Complexity

D · Edges

E · Code

F · Tradeoff

G · Score

Phase A — Clarify

Ask questions about input bounds, types, and edge constraints.

Ask the coach clarifying questions about the problem.

When you've covered this phase, advance to the next.