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54. Simplify Path

mediumAsked at Salesforce

Convert a Unix-style file path to its canonical form. Salesforce uses this to test stack-based string processing — analogous to their record-hierarchy canonicalization.

By Alex Chen, Founder, InterviewChamp.AI · Last verified

Source citations

Public interview reports confirming this problem appears in Salesforce loops.

  • Glassdoor (2026-Q1)— Salesforce uses path-canonicalization in their content-management module.
  • LeetCode Discuss (2025)— Tests split + stack pattern.

Problem

Given a string path, which is an absolute path (starting with a slash '/') to a file or directory in a Unix-style file system, convert it to the simplified canonical path. The canonical path should have the following format: starts with '/', any two directories are separated by '/', does not end with '/' (unless root). It should also be the shortest string representing the absolute path. Return the simplified canonical path.

Constraints

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

Examples

Example 1

Input
path = "/home/"
Output
"/home"

Example 2

Input
path = "/../"
Output
"/"

Example 3

Input
path = "/home//foo/"
Output
"/home/foo"

Example 4

Input
path = "/a/./b/../../c/"
Output
"/c"

Approaches

1. Manual character walk

Walk char by char; build segments; handle . and .. inline.

Time
O(n)
Space
O(n)
// Verbose. Salesforce prefers split + stack.

Tradeoff: Too much state. Split first.

2. Split on '/' and stack-process

Split by '/'. For each segment: '..' pops stack; '.' or '' ignored; else push. Join with '/'.

Time
O(n)
Space
O(n)
function simplifyPath(path) {
  const stack = [];
  for (const part of path.split('/')) {
    if (part === '' || part === '.') continue;
    if (part === '..') stack.pop();
    else stack.push(part);
  }
  return '/' + stack.join('/');
}

Tradeoff: Concise and clear. Split handles repeated slashes naturally (gives empty segments which we skip).

Salesforce-specific tips

Salesforce uses path-canonicalization in their content-management module (folder hierarchies, library structures). They grade on whether you skip empty segments AND single dots. Bonus signal: discuss the '..' behavior at root — popping an empty stack should be a no-op, which is what stack.pop() does naturally on empty arrays.

Common mistakes

  • Pushing the '/' itself onto the stack — get '//' separator bugs.
  • Returning '/' + stack.join('/') when stack is empty — gives just '/', which is correct, but easy to miss.
  • Treating '...' (three dots) as '..' — only '..' is the parent reference; '...' is a valid filename.

Follow-up questions

An interviewer at Salesforce may pivot to one of these next:

  • Decode URL paths.
  • Implement cd command behavior (relative vs absolute).
  • Resolve symbolic links given a map.

Solve it now

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Output

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FAQ

Why does split('/') handle empty segments correctly?

Repeated slashes (//) produce empty strings between them. Skipping empty strings collapses runs of slashes naturally.

What happens at root with '..'?

stack.pop() on an empty stack is a no-op in JavaScript. Result is still '/' which is the correct canonical root.

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