Find if an array contains at least two elements which differ by 1

Problem

Write a javascript function:

function solution(arr);

that, given an array arr of n positive integers returns 1 if arr contains at least two items which differ by 1 otherwise 0.

Examples

1. Given, arr=[9], the method should return 0.
2. Given, arr=[5,4], the method should return 1.
3. Given, arr=[12, 2, 9, 13, 15], the method should return 1. Pair of items which differ by 1 is (12, 13).
4. Given, arr=[5, 11, 9, 6, 10], the method should return 1. Pairs of items which differ by 1 are (5, 6), (11, 10) and (8, 9).
5. Given, arr=[6, 6, 6, 6, 6], the method should return 0. There are no two items in array whose values differ by 1.

Write an algorithm for the following consideration

• n is a positive integer in the range of 1..,99,999].
• each items of an array is a positive integer in the range 1...99,99,99,999]

Solution

function solution(arr) {
  if (arr && arr.length > 0) {
    let visitedNum = new Set();

    let result = arr.every((num) => {
      if (visitedNum.has(num - 1) || visitedNum.has(num + 1)) {
        return 0;
      }

      visitedNum.add(num);

      return 1;
    });

    return !result;
  }

  return 0;
}

The solution above is pretty self-explanatory.

Result

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