Intersection of Two Arrays

Author: shashankvishwakarma

src/main/java/leetcode/easy/IntersectionOfTwoArrays.java

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+package leetcode.easy;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+
+/**
+ * https://leetcode.com/problems/intersection-of-two-arrays-ii/description/
+ * <p>
+ * Example 1:
+ * Input: nums1 = [1,2,2,1], nums2 = [2,2]
+ * Output: [2,2]
+ * <p>
+ * Example 2:
+ * Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4]
+ * Output: [4,9]
+ */
+public class IntersectionOfTwoArrays {
+
+    public static void main(String[] args) {
+        // Test case 1
+        int[] nums1 = {1, 2, 2, 1};
+        int[] nums2 = {2, 2};
+        int[] result1 = intersect(nums1, nums2);
+        System.out.print("Intersection of nums1 and nums2: ");
+        for (int num : result1) {
+            System.out.print(num + " ");
+        }
+        System.out.println();
+
+        // Test case 2
+        int[] nums3 = {4, 9, 5};
+        int[] nums4 = {9, 4, 9, 8, 4};
+        int[] result2 = intersect(nums3, nums4);
+        System.out.print("Intersection of nums3 and nums4: ");
+        for (int num : result2) {
+            System.out.print(num + " ");
+        }
+        System.out.println();
+    }
+
+    public static int[] intersect(int[] nums1, int[] nums2) {
+        HashMap<Integer, Integer> map = new HashMap<>();
+        ArrayList<Integer> resultList = new ArrayList<>();
+
+        // Count frequency of each element in nums1
+        for (int num : nums1) {
+            map.put(num, map.getOrDefault(num, 0) + 1);
+        }
+
+        // Find intersection with nums2
+        for (int num : nums2) {
+            if (map.containsKey(num) && map.get(num) > 0) {
+                resultList.add(num);
+                map.put(num, map.get(num) - 1); // Decrease the count in the map
+            }
+        }
+
+        // Convert ArrayList to int array
+        int[] result = new int[resultList.size()];
+        for (int i = 0; i < resultList.size(); i++) {
+            result[i] = resultList.get(i);
+        }
+
+        return result;
+    }
+}