First solution in Clear category for Double Substring by m.kurapov
length of the longest substring that non-overlapping repeats more than once.
longest = 0
len_line = len(line)
for i in range(len_line):
while i+longest*2 < len_line and line.count(line[i:i+longest+1]) > 1:
longest += 1
Feb. 18, 2020