Recursion Problem

Time Complexity: O(N) N is number of words in input

def lengthLongestPath(input):
    filepathes = []
    path = []
    foo(input.split("\n"), 0, path, filepathes)
    if len(filepathes) == 0:
        return 0
    lens = map(lambda path: len(path), filepathes)
    print(filepathes)
    return max(lens)

def foo(arr, index, path, filepathes):
    if len(arr) == index:
        return
    depth = arr[index].count("\t")
    dirname = arr[index].strip("\t")
    if path:
        rootpath = path[:depth]
    else:
        rootpath = []

    if arr[index].find(".") != -1:
        filename = arr[index].strip("\t")
        rootpath.append(filename)
        filepathes.append('/'.join(rootpath))
        rootpath.pop()
        foo(arr, index + 1, rootpath, filepathes)
        #return

    else:
        rootpath.append(dirname)
        foo(arr, index + 1, rootpath, filepathes)

input = "dir\n\tsubdir1\n\tsubdir2\n\t\tfile.ext" # 20
print(lengthLongestPath(input))

input = "dir\n\tsubdir1\n\t\tfile1.ext\n\t\tsubsubdir1\n\tsubdir2\n\t\tsubsubdir2\n\t\t\tfile2.ext" # 32
print(lengthLongestPath(input))

input = "file1.txt\nfile2.txt\nlongfile.txt" # 12
print(lengthLongestPath(input))

input ="dir\n        file.txt"
print(lengthLongestPath(input)) # 16