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

Problem Summary

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

Solution Approach

• Easy problem. Use a map to count the frequency of each element. Then add up all elements with a frequency of 1, and finally output the accumulated sum.

Code

package leetcode

func sumOfUnique(nums []int) int {
	freq, res := make(map[int]int), 0
	for _, v := range nums {
		if _, ok := freq[v]; !ok {
			freq[v] = 0
		}
		freq[v]++
	}
	for k, v := range freq {
		if v == 1 {
			res += k
		}
	}
	return res
}