388. Longest Absolute File Path

class Solution(object):
    def lengthLongestPath(self, input):
        """
        :type input: str
        :rtype: int
        """
        maxlen=0
        pathlen={0:0}
        for line in input.splitlines():
            name=line.lstrip('\t')
            depth=len(line)-len(name)
            if '.' in name:
                maxlen=max(maxlen,pathlen[depth]+len(name))
            else:
                pathlen[depth+1]=pathlen[depth]+len(name)+1
        return maxlen