find the single integer

Question

Given an array of integers, all integers appear twice except one integer, could you quickly target it ?

const arr = [10, 2, 2 , 1, 0, 0, 10]
findSingle(arr) // 1

What is time & space cost of your approach ? Could you do better ?

Code

/**
 * @param {number[]} arr
 * @returns number
 */
function findSingle(arr) {
  // your code here
}

Source

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