/**
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
Related Topics并查集 | 数组 | 哈希表
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*/
//leetcode submit region begin(Prohibit modification and deletion)
class Solution {
public int longestConsecutive(int[] nums) {
Set<Integer> hashSet = new HashSet<>();
for (int num : nums) {
hashSet.add(num);
}
int result = 0;
for (int value : hashSet) {
if (!hashSet.contains(value - 1)) {
int len = 1;
int i = value + 1;
while (hashSet.contains(i)) {
len++;
i++;
}
if (len > result) {
result = len;
}
}
}
return result;
}
}
//leetcode submit region end(Prohibit modification and deletion)
