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
class Solution {
public int longestConsecutive(int[] nums) {
HashMap<Integer,Boolean> hm = new HashMap<>();
for(int i=0;i<nums.length;i++){
hm.put(nums[i],false);
}
for(int key : hm.keySet()){
if(hm.containsKey(key-1)==false){
hm.put(key,true);
}
}
int max = 0 ;
for(int key : hm.keySet()){
int k=1 ;
if(hm.get(key)==true){
while(hm.containsKey(key+k)==true){
k++;
}
}
max = Math.max(max,k);
}
return max ;
}
}
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