Longest Absolute File Path

Suppose we have a file system that stores both files and directories.

If we were to write this representation in code, it will look like this: "dir\n\tsubdir1\n\t\tfile1.ext\n\t\tsubsubdir1\n\tsubdir2\n\t\tsubsubdir2\n\t\t\tfile2.ext". Note that the '\n' and '\t' are the new-line and tab characters.

Every file and directory has a unique absolute path in the file system, which is the order of directories that must be opened to reach the file/directory itself, all concatenated by '/'s. Using the above example, the absolute path to file2.ext is "dir/subdir2/subsubdir2/file2.ext". Each directory name consists of letters, digits, and/or spaces. Each file name is of the form name.extension, where name and extension consist of letters, digits, and/or spaces.

Given a string input representing the file system in the explained format, return the length of the longest absolute path to a file in the abstracted file system. If there is no file in the system, return 0. 

Example:

Input: input = "file1.txt\nfile2.txt\nlongfile.txt"
Output: 12
Explanation: There are 3 files at the root directory.
Since the absolute path for anything at the root directory is just the name itself, the answer is "longfile.txt" with length 12.

Approach:

C++

#include <bits/stdc++.h>
using namespace std;

int lengthLongestPath(string input)
{
    stringstream ss(input);
    string line;
    unordered_map<int, int> map = {{0, 0}};
    int res = 0;

    while (getline(ss, line, '\n'))
    {
        auto tab = line.find_last_of('\t');
        int level = tab == string::npos ? 0 : tab + 1;
        int len = line.substr(level).length();
        if (line.find('.') != string::npos)
        {
            res = max(res, map[level] + len);
        }
        else
        {
            map[level + 1] = map[level] + len + 1;
        }
    }
    return res;
}

int main()
{
    string input = "file1.txt\nfile2.txt\nlongfile.txt";

    cout << lengthLongestPath(input);

    return 0;
}