#1346 - Check If N and Its Double Exist

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Array Hash Table Sorting Binary Search Two Pointers

Problem Description

Given an array arr of integers, check if there exist two indices i and j such that:

i != j
0 <= i, j < arr.length
arr[i] == 2 * arr[j]

Solution

/**
 * @param {number[]} arr
 * @return {boolean}
 */
var checkIfExist = function(arr) {
  const set = new Set();

  for (const num of arr) {
    if (set.has(num * 2) || set.has(num / 2)) {
      return true;
    }
    set.add(num);
  }

  return false;
};