Intersection of two arrays
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import java.util.*;
class Main {
/*
Write a function or program that takes two arrays of integers as input and
returns an array containing all the elements that are common to both input arrays (i.e., the intersection).
Array 1: [1, 2, 2, 1]
Array 2: [2, 2]
*/
// Store the elements of array1 using HashSet
// iterate through the other array to find the common elements
// check each element of other element is stored in the HashSet.
public static int[] findCommonElement(int[] array1, int[] array2){
Set<Integer> set = new HashSet<>();
Set<Integer> result = new HashSet<>();
// store element of array1
for(int e : array1){
set.add(e);
}
// iterate array2 to find common e
for(int e : array2){
if(set.contains(e)){
result.add(e);
}
}
// convert the result set into an array
int[] intersection = new int[result.size()];
int index = 0;
for (int num : result){
intersection[index++] = num;
}
return intersection;
}
public static void main(String[] args) {
int[] array1 = {1,2,2,1};
int[] array2 = {2,2};
int[] isCommon = findCommonElement(array1,array2);
System.out.println(Arrays.toString(isCommon));
}
/*
Time Complexity: O(m+n), where m and n are the sizes of the input arrays.
Space Complexity: O(m+k), where m is the number of unique elements in the first array, and
k is the size of the intersection array.
*/
}
Java
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