Find the element that appear once in array

Problem
Given an array with items.
each item in the array appear twice except once element.
E.g [1,4,3,4,1]
here the element 3 appear only once hence it should be returned.
Solution
Prerequisite knowledge hashMap or Dictionary.
How do you find the element.
Using Dictionary.

1 Create a Dictionary.
2 Assign the key of the dictionary as the array items, and the value as count of times it appears in the array.
3 Return the dictionary item with the value of 1.

Create items dictionary
Loop through the array i = 0,....n = length of the array-1.
If the array[i] is not a key in the items dictionary create a key with value of 1
if the array[i] is a key in the dictionary increment the value by 1.

Loop through the dictionary of items to get the key with 1 as value and return it, if all are more than one.

return -1.

Time Complexity O(n)
Because we are looping through the array n times.
Space Complexity O(n)
Because we are creating a map with at worst case n keys.