LeetCode-in-Java
2150. Find All Lonely Numbers in the Array
Medium
You are given an integer array nums. A number x is lonely when it appears only once, and no adjacent numbers (i.e. x + 1 and x - 1) appear in the array.
Return all lonely numbers in nums. You may return the answer in any order.
Example 1:
Input: nums = [10,6,5,8]
Output: [10,8]
Explanation:
-
10 is a lonely number since it appears exactly once and 9 and 11 does not appear in nums.
-
8 is a lonely number since it appears exactly once and 7 and 9 does not appear in nums.
-
5 is not a lonely number since 6 appears in nums and vice versa.
Hence, the lonely numbers in nums are [10, 8].
Note that [8, 10] may also be returned.
Example 2:
Input: nums = [1,3,5,3]
Output: [1,5]
Explanation:
-
1 is a lonely number since it appears exactly once and 0 and 2 does not appear in nums.
-
5 is a lonely number since it appears exactly once and 4 and 6 does not appear in nums.
-
3 is not a lonely number since it appears twice.
Hence, the lonely numbers in nums are [1, 5].
Note that [5, 1] may also be returned.
Constraints:
1 <= nums.length <= 1050 <= nums[i] <= 106
Solution
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
public class Solution {
public List<Integer> findLonely(int[] nums) {
List<Integer> ans = new ArrayList<>();
HashMap<Integer, Integer> m = new HashMap<>();
for (int i : nums) {
m.put(i, m.getOrDefault(i, 0) + 1);
}
for (int i : nums) {
if (m.get(i) == 1 && !m.containsKey(i - 1) && !m.containsKey(i + 1)) {
ans.add(i);
}
}
return ans;
}
}