Largest distance in an integer list

Question

How to find the maximum distance between two same elements/integers of a list in python. e.g. if a list is [1,3,3,5,6,4,8,6,0,3,5] Output would be 8 (distance b/w 3's is maximum here)

Answer 1

You can use a dictionary where for each value you save the indices.

from collections import defaultdict

d = defaultdict(list)

for i,el in enumerate(l):
    d[el].append(i)

max_dist = max(d[k][-1]-d[k][0] for k in d)