longest-absolute-file-path

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

public class Solution {
    public int lengthLongestPath(String input) {
        Stack<Integer> stk = new Stack<Integer>();
        int left = 0;
        int curStrlen = 0;
        int curTab = 0;
        int ret = 0;
        boolean hasDot = false;
        boolean isFile = false;
        
        for (int i=0; i<input.length(); i++) {
            // \n
            if (input.charAt(i) == 10) {

                curStrlen = i-left;
                if (!stk.empty()) {
                    curStrlen += 1 + stk.peek();
                }
                    
                if (isFile && curStrlen > ret) {
                    ret  = curStrlen;
                }
                stk.push(curStrlen);
                hasDot = false;
                isFile = false;
                curTab = 0;
                left = -1;
            }
            // \t
            else if (input.charAt(i) == 9 && curTab < stk.size()) {
                curTab++;
            }
            else if (input.charAt(i) == ' ' && i+3 < input.length() &&
                     input.substring(i, i+4).equals("    ") && curTab < stk.size()) {
                curTab++;
                i += 3;
            }
            else {
                if (left == -1) {
                    int stkLen = stk.size();
                    for (int j=0; j<stkLen-curTab; j++) {
                        stk.pop();
                    }
                    left = i;
                }
                if (input.charAt(i) == '.') {
                    hasDot = true;
                }
                else {
                    if (hasDot) {
                        isFile = true;
                    }
                }
            }

        }
        
        curStrlen = input.length()-left;
        if (!stk.empty()) {
            curStrlen += 1 + stk.peek();
        }
        if (isFile && curStrlen > ret) {
            ret = curStrlen;
        }
        return ret;
    }
}