128. Longest Consecutive Sequence
package LeetCode_128 /** * 128. Longest Consecutive Sequence * https://leetcode.com/problems/longest-consecutive-sequence/description/ * * Given an unsorted array of integers, find the length of the longest consecutive elements sequence. Your algorithm should run in O(n) complexity. Example: Input: [100, 4, 200, 1, 3, 2] Output: 4 Explanation: The longest consecutive elements sequence is [1, 2, 3, 4]. Therefore its length is 4. * */ class Solution { fun longestConsecutive(nums: IntArray): Int { val set = HashSet<Int>() for (item in nums) { set.add(item) } var res = 0 for (num_ in nums) { var num = num_ //find out the lower bound var left = 0 //if left one of current num not exist, scan in set to find out the upper bound if (!set.contains(num - 1)) { while (set.contains(num++)) { left++ } res = Math.max(res, left) } } return res } }