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;    }}