LeetCode_350. Intersection of Two Arrays II

350. Intersection of Two Arrays II

Easy

Given two arrays, write a function to compute their intersection.

Example 1:

Input: nums1 = [1,2,2,1], nums2 = [2,2]
Output: [2,2]

Example 2:

Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4]
Output: [4,9]

Note:

• Each element in the result should appear as many times as it shows in both arrays.
• The result can be in any order.

Follow up:

• What if the given array is already sorted? How would you optimize your algorithm?
• What if nums1's size is small compared to nums2's size? Which algorithm is better?
• What if elements of nums2 are stored on disk, and the memory is limited such that you cannot load all elements into the memory at once?

package leetcode.easy;

public class IntersectionOfTwoArraysII {
	private static void print_arr(int[] nums) {
		for (int num : nums) {
			System.out.print(num + " ");
		}
		System.out.println();
	}

	public int[] intersect(int[] nums1, int[] nums2) {
		int i = 0, j = 0, k = 0;
		int len = nums1.length < nums2.length ? nums1.length : nums2.length;
		int[] nums = new int[len];
		java.util.Arrays.sort(nums1);
		java.util.Arrays.sort(nums2);
		while (i < nums1.length && j < nums2.length) {
			if (nums1[i] < nums2[j]) {
				i++;
			} else if (nums1[i] > nums2[j]) {
				j++;
			} else {
				nums[k++] = nums1[i];
				i++;
				j++;
			}
		}
		return java.util.Arrays.copyOf(nums, k);
	}

	@org.junit.Test
	public void test1() {
		int[] nums1 = { 1, 2, 2, 1 };
		int[] nums2 = { 2, 2 };
		print_arr(intersect(nums1, nums2));
	}

	@org.junit.Test
	public void test2() {
		int[] nums1 = { 4, 9, 5 };
		int[] nums2 = { 9, 4, 9, 8, 4 };
		print_arr(intersect(nums1, nums2));
	}
}