Union and Intersection of Arrays

Problem Statement

Union of two arrays | Practice | GeeksforGeeks Intersection of Two Arrays - LeetCode

Pattern:

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Union Solution

public int[] doUnion (int a[], int n, int b[], int m){
	HashSet<Integer> set = new HashSet<>();
	for(int num: a) set.add(num);
	for(int num: b) set.add(num);
	
	return set.stream().mapToInt(i->i).toArray();   // to return intersection array
	//return set.size();
}

Intersection Solution

public int[] intersection (int[] nums1, int[] nums2){
	HashSet<Integer> set = new HashSet<>();
	HashSet<Integer> intersect = new HashSet<>();
	
	for(int num : nums1) set.add(num);
	for(int num : nums2)
		if(set.contains(num)) intersect.add(num);
	
	return intersect.stream().mapToInt(i -> i).toArray();
}

Better Solution ?

Intersection of two sorted Linked lists | Practice | GeeksforGeeks when arrays are sorted, u can use 2 pointers and some simple logic like GFG Intersection of Two Sorted LLs