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Longest Consecutive Sequence
MediumVerifiedSetArrayHash Map~25 min
Given an unsorted array nums, return the length of the longest run of consecutive integers.
Use a set. Start counting only from values with no predecessor in the set, so each run is walked once — O(n).
The input arrives as a single array nums.
Examples
in[100, 4, 200, 1, 3, 2]
out4
The run 1, 2, 3, 4 has length 4.
in[]
out0
No elements, no sequence.
Constraints
- 0 ≤ nums.length ≤ 10⁵
- -10⁹ ≤ nums[i] ≤ 10⁹
- Target: O(n) time
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