Find the longest path file

February 18, 2023

Name: Moch Lutfi
Twitter: @kaptenupi

Problem

Suppose we represent our file system as a string. For example, the string "user\n\tpictures\n\tdocuments\n\t\tnotes.txt" represents:

user
    pictures
    documents
        notes.txt

The directory user contains an empty sub-directory pictures and a sub-directory documents containing a file notes.txt.

The string "user\n\tpictures\n\t\tphoto.png\n\t\tcamera\n\tdocuments\n\t\tlectures\n\t\t\tnotes.txt" represents:

user
    pictures
        photo.png
        camera
    documents
        lectures
            notes.txt

The directory user contains two sub-directories pictures and documents. pictures contains a file photo.png and an empty second-level sub-directory camera. documents contains a second-level sub-directory lectures containing a file notes.txt.

We want to find the longest (as determined by the number of characters) absolute path to a file within our system. For example, in the second example above, the longest absolute path is "user/documents/lectures/notes.txt", and its length is 33 (not including the double quotes).

Given a string representing the file system in this format, return the length of the longest absolute path to a file in the abstracted file system. If there is not a file in the file system, return 0.

Notes:

Due to system limitations, test cases use form feeds ('\f', ASCII code 12) instead of newline characters.
File names do not contain spaces at the beginning.

Example

For fileSystem = "user\f\tpictures\f\tdocuments\f\t\tnotes.txt", the output should be
solution(fileSystem) = 24.

The longest path is "user/documents/notes.txt", and it consists of 24 characters.

Constraints

File system in the format described above. It is guaranteed that:

the name of a file contains at least a . and an extension;
the name of a directory or sub-directory does not contain a ..

Note: Due to system limitations, newline characters are given as form feeds ('\f', ASCII code 12) in our test cases.

Guaranteed constraints:
1 ≤ fileSystem.length ≤ 6310.

Solution

import "strings"
func solution(fileSystem string) int {
    lines := strings.Split(fileSystem, "\f")
    stack := []string{}
    maxLen := 0
    for _, line := range lines {
        tabs := strings.Count(line, "\t")
        // trim \t to get name
        name := strings.TrimLeft(line, "\t")
        for len(stack) > tabs {
            stack = stack[:len(stack)-1] // pop stack
        }
        if strings.Contains(name, ".") {
            currLen := len(strings.Join(append(stack, name), "/"))
            if currLen > maxLen {
                maxLen = currLen
            }
        } else {
            stack = append(stack, name)
        }
    }
    return maxLen
}

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