Longest Absolute file path

LongestAbsoluteFilePath.java

// https://leetcode.com/problems/longest-absolute-file-path/description/

class Solution {
  class FileLevel {
    int level; int len;
  }

  public int countOfCharacter(String s, Character seq){
    int count = 0;
    for(int i = 0 ;i < s.length();i++){
      if(s.charAt(i) == seq){
        count += 1;
      } else {
        return count;
      }
    }
    return count;
  }

  public int lengthLongestPath(String input) {
    String[] tokens = input.split("\n");
    Stack<FileLevel> levelStack = new Stack<FileLevel>();
    int maxLen = 0;
    for(String token: tokens){
      int level = countOfCharacter(token, '\t');
      if(token.contains(".")){
        while(!levelStack.empty() && level <= levelStack.peek().level){
          levelStack.pop();
        }
        int prevLevel = levelStack.empty() ? 0 : levelStack.peek().len;
        maxLen = Math.max(maxLen, prevLevel + token.length() - level);
      } else {
        while(!levelStack.empty() && level <= levelStack.peek().level){
          levelStack.pop();
        }
        FileLevel fl = new FileLevel();
        int prevLen = levelStack.empty() ? 0 : levelStack.peek().len;
        fl.len = prevLen + token.length() + 1 - level;  // .. +1 is for the trailing `/` character sequence
        fl.level = level;
        levelStack.push(fl);
      }
    }
    return maxLen;
  }
}