Find the intersection of two integer lists

Question

N · Accepted Answer

why do you need this big code?

Try to be simple while explaining simple ideas..

1) add list1 elements to hash.
2) iterate through list2. check if the item is present in hash and add to output list.
3) return output list.

Best way is to leave it here and ask politely if he wants to code this simple naive idea?
Over explaining simple things will cast impression of small knowledge.

Harry · Answer

Share a blog on this topic:

http://codercareer.blogspot.com/2011/11/no-24-intersection-of-sorted-arrays.html

Kanika · Answer

I tried to implement it using HashTable technique

public ArrayList intersection(int list1[], int list2[]) {
		int i, max = 0, min = 0;

		Hashtable hash;
		ArrayList list = new ArrayList();
		if (list1.length > list2.length) {
			hash = new Hashtable(list1.length, list1.length);
			max = list1.length;
			min = list2.length;
		} else {
			hash = new Hashtable(list2.length, list2.length);
			max = list2.length;
			min = list1.length;
		}
		for (i = 0; i < max; i++) {
			if (max == list1.length)
				hash.put(list1[i], list1[i]);
			else
				hash.put(list2[i], list2[i]);
		}

		for (i = 0; i < min; i++) {
			if (min == list1.length) {
				if (hash.put(list1[i], list1[i]) != null) {
					list.add(list1[i]);
				}
			} else {
				if (hash.put(list2[i], list2[i]) != null) {
					list.add(list2[i]);
				}
			}
		}
     return list;
	}

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