071. Simplify Path

At a Glance

Topic: stack
Pattern: Stack (token processing)
Difficulty: Medium
Companies: Amazon, Google, Meta, Microsoft, Bloomberg
Frequency: Medium
LeetCode: 71

Problem (one-liner)

Given a Unix-style absolute path string, return its simplified canonical form: collapse ., resolve .. against parent, drop redundant slashes, keep leading /.

Recognition Cues

Slash-separated tokens
".." pops parent directory
"" and "." are no-ops in most rules

Diagram

At-a-glance flow (replace with problem-specific Mermaid as you refine this note). camelCase node IDs; no spaces in IDs.

Loading diagram…

Approaches

Brute force — split, list manipulation with index pointer — O(n) but verbose.
Better — stack of path components — O(n) time / O(n) space.
Optimal — split("/") + filter rules — same complexity, clearest.

Optimal Solution

Go

import "strings"

func simplifyPath(path string) string {
	parts := strings.Split(path, "/")
	stack := make([]string, 0, len(parts))
	for _, part := range parts {
		if part == "" || part == "." {
			continue
		}
		if part == ".." {
			if len(stack) > 0 {
				stack = stack[:len(stack)-1]
			}
		} else {
			stack = append(stack, part)
		}
	}
	return "/" + strings.Join(stack, "/")
}

JavaScript

function simplifyPath(path) {
	const parts = path.split('/');
	const stack = [];
	for (const part of parts) {
		if (part === '' || part === '.') {
			continue;
		}
		if (part === '..') {
			if (stack.length > 0) {
				stack.pop();
			}
		} else {
			stack.push(part);
		}
	}
	return '/' + stack.join('/');
}