Sum of Unique Elements

ArrayCountingHash Table

Given an array of integers, return the sum of all the unique elements. An element is considered unique if it appears exactly once in the array.

Example 1

Input

[
  4,
  4,
  5,
  6,
  8,
  5,
  9
]

Output

Explanation. The unique elements are 6, 8, and 9. The sum is 6+8+9=23.

Example 2

Input

[
  1,
  1,
  1,
  1
]

Output

Explanation. There are no unique elements in the array. Therefore, the sum is 0.

Example 3

Input

[
  7,
  7,
  8,
  3,
  3
]

Output

Explanation. The only unique element is 8.

Example 4

Input

[
  5
]

Output

Explanation. The array contains only one element, which is unique by default. The sum is 5.

Follow-up: How would you solve this problem if a modification to the input array is allowed? What if it isn't?

Constraints:

The input array contains at least one element. All elements are integers.