#2215 - Find the Difference of Two Arrays

EasyHash Map / Set

Given two 0-indexed integer arrays nums1 and nums2, return a list answer of size 2 where:

• answer[0] is a list of all distinct integers in nums1 that are not in nums2.
• answer[1] is a list of all distinct integers in nums2 that are not in nums1.

The integers in each list may be returned in any order.

Input	Output
nums1 = [1,2,3], nums2 = [2,4,6]	[[1,3],[4,6]]
nums1 = [1,2,3,3], nums2 = [1,1,2,2]	[[3],[]]

Solution Space

Try it

/**
 * Returns two lists: values unique to nums1, and values unique to nums2.
 *
 * @param nums1 First integer array
 * @param nums2 Second integer array
 * @returns     [distinctInNums1Only, distinctInNums2Only]
 */
export function findDifference(
  nums1: number[],
  nums2: number[],
): [number[], number[]] {
  const set1 = new Set(nums1);
  const set2 = new Set(nums2);

  return [
    [...set1].filter((n) => !set2.has(n)),
    [...set2].filter((n) => !set1.has(n)),
  ];
}

Approach: hash-set – convert both arrays to sets for O(1) lookups, then filter each set for elements absent from the other.

Time: O(n + m) – building the sets is O(n + m); filtering is O(n + m) in total.

Space: O(n + m) – storage for both sets and the output arrays.

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