1748. Sum of Unique Elements

Problem

You are given an integer array nums. The unique elements of an array are the elements that appear exactly once in the array.

Return **the *sum* of all the unique elements of **nums.

  Example 1:

Input: nums = [1,2,3,2]
Output: 4
Explanation: The unique elements are [1,3], and the sum is 4.

Example 2:

Input: nums = [1,1,1,1,1]
Output: 0
Explanation: There are no unique elements, and the sum is 0.

Example 3:

Input: nums = [1,2,3,4,5]
Output: 15
Explanation: The unique elements are [1,2,3,4,5], and the sum is 15.

  Constraints:

• 1 <= nums.length <= 100

• 1 <= nums[i] <= 100

Solution (Java)

class Solution {
    public int sumOfUnique(int[] nums) {
        Map<Integer, Integer> map = new HashMap<>();
        int sum = 0;
        for (int num : nums) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            if (entry.getValue() == 1) {
                sum += entry.getKey();
            }
        }
        return sum;
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).