Sum of Unique Elements

ArrayCountingHash Table

Given an array of integers, compute the sum of all unique elements in the array. An element is considered unique if it does not have any duplicates in the array.

Example 1

Input

[
  4,
  5,
  5,
  4,
  7
]

Output

Explanation. Elements 4 and 5 have duplicates. The sum of the unique element (7) is 7.

Example 2

Input

[
  6,
  3,
  9,
  6,
  3
]

Output

Explanation. All elements except 9 have duplicates. Thus, the sum is 9.

Example 3

Input

[
  1,
  2,
  3,
  4,
  5
]

Output

Explanation. No duplicates are found, hence the sum of all elements is 15.

Example 4

Input

[
  -1,
  -1,
  2,
  2,
  0
]

Output

Explanation. Only 0 is unique, thus the sum is 0.

Follow-up: Can you solve this problem in O(n) time complexity using extra space?

Constraints:

1. The input array can contain positive and negative numbers. 2. The size of the input array will be at least 1.

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