Hash maps and sets · stretch

Longest run of consecutive numbers

Write longest_run(nums) returning the length of the longest run of consecutive whole numbers in the list, in any order: [100, 4, 200, 1, 3, 2] has 1, 2, 3, 4, so 4.

Put everything in a set. A run starts at a number whose predecessor is missing; count up from there.

right answers
arguments left as they should be
fast enough at scale
without sorted, sort

def longest_run(nums):
    best = 0
    for n in nums:
        length = 1
        while n + length in nums:
            length += 1
        best = max(best, length)
    return best

Run adds print(longest_run([100, 4, 200, 1, 3, 2])) after your code, to try it.

Stuck on the idea rather than the code? The Choosing a key lesson walks through it.