LeetCode 388: Longest Absolute File Path

class Solution {
    public int lengthLongestPath(String input) {
        if (input.length() == 0) return 0;
        String[] layers = input.split("\n");
        int[] stack = new int[layers.length + 1];
        int result = 0;
        for (String s : layers) {
            int level = s.lastIndexOf("\t") + 1, current = stack[level + 1] = stack[level] + s.length() - level + 1; // Find how many \t, which mean it belongs to which level. stack[level + 1] = stack[level] + s.length() - 1evel + 1 is calculate current level length by removing \t and update the prefix for next level
            if (s.contains(".")) result = Math.max(result, current - 1); // Check the last file.
        }
        return result;
    }
}