AlgoDaily - Single Lonely Number

Single Lonely Number (Easy)

Good morning! Here's our prompt for today.

You may see this problem at Google, Flipkart, Twitter, Vmware, Adobe, Wework, Ebay, Groupon, Tableau Software, Workday, Jane Street, Servicetitan, Squarespace, Keeptruckin, Zoom, Tradeshift, Baidu, New Relic, and Qualtrics.

In a given array of numbers, one element will show up once and the others will each show up twice. Can you find the number that only appears once in O(n) linear time? Bonus points if you can do it in O(1) space as well.

SNIPPET

1lonelyNumber([4, 4, 6, 1, 3, 1, 3])
2// 6
3
4lonelyNumber([3, 3, 9])
5// 9

Constraints

Length of the array <= 100,000
The values of the array will be between -1,000,000,000 and 1,000,000,000

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​
 
var assert = require('assert');
​
function lonelyNumber(numbers) {
  // Fill in this method
  return numbers;
}
​
try {
  assert.equal(lonelyNumber([4, 4, 6, 1, 3, 1, 3]), 6);
​
  console.log(
    'PASSED: ' + '`lonelyNumber([4, 4, 6, 1, 3, 1, 3])` should return `6`'
  );
} catch (err) {
  console.log(err);
}
​
try {
  assert.equal(lonelyNumber([3, 3, 9]), 9);
​
  console.log('PASSED: ' + '`lonelyNumber([3, 3, 9])` should return `9`');
} catch (err) {
  console.log(err);
}
​
try {
  assertIsFunction(lonelyNumber, '`lonelyNumber` is a function');

OUTPUT

Results will appear here.