LeetCode-in-All
128. Longest Consecutive Sequence
Medium
Given an unsorted array of integers nums, return the length of the longest consecutive elements sequence.
You must write an algorithm that runs in O(n) time.
Example 1:
Input: nums = [100,4,200,1,3,2]
Output: 4
Explanation: The longest consecutive elements sequence is [1, 2, 3, 4]. Therefore its length is 4.
Example 2:
Input: nums = [0,3,7,2,5,8,4,6,0,1]
Output: 9
Constraints:
0 <= nums.length <= 105-109 <= nums[i] <= 109
Solution
import java.util.PriorityQueue
class Solution {
fun longestConsecutive(nums: IntArray): Int {
if (nums.isEmpty()) {
return 0
}
val queue = PriorityQueue<Int>()
nums.forEach {
queue.add(it)
}
var lastNum = Integer.MIN_VALUE
var length = 0
var maxLength = 1
while (queue.isNotEmpty()) {
val num = queue.poll()
if (num == lastNum) {
continue
}
length++
if (num - lastNum > 1) {
length = 1
}
lastNum = num
maxLength = maxOf(maxLength, length)
}
return maxLength
}
}