Reviewed by Aditya Kumar · Last reviewed 2026-03-24
Hash set; only count from sequence start (no n-1 in set). Python: s=set(nums); best=0; for n in s: if n-1 not in s: c,x=1,n; while x+1 in s: c+=1; x+=1; best=max(best,c); return best. Key: only start when n-1 not in set (avoids recounting)....
Hash set; only count from sequence start (no n-1 in set). Python: s=set(nums); best=0; for n in s: if n-1 not in s: c,x=1,n; while x+1 in s: c+=1; x+=1; best=max(best,c); return best. Key: only start when n-1 not in set (avoids recounting). O(n) time, O(n) space.
Red Flag: O(n log n) sort solution. Pro-Move: 'Set + only start from sequence head = O(n); explain why we skip when n-1 in set.'
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