349. Intersection of Two Arrays leetCode

 Given two integer arrays nums1 and nums2, return an array of their intersection. Each element in the result must be unique and you may return the result in any order.


Example 1:


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

Output: [2]

Example 2:


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

Output: [9,4]

Explanation: [4,9] is also accepted.


Approach 1:

import java.util.*;

class Solution {
    public int[] intersection(int[] nums1, int[] nums2) {

        //  Step 1: Sort both arrays (Optional but helpful for two-pointer approach)
        Arrays.sort(nums1);
        Arrays.sort(nums2);  

        // Step 2: Use a HashSet to store the intersection (unique values only)
        Set<Integer> set = new HashSet<>();

        // Step 3: Initialize two pointers
        int i = 0; // pointer for nums1
        int j = 0; // pointer for nums2

        int n1 = nums1.length;
        int n2 = nums2.length;

        // Step 4: Use two-pointer technique to find common elements
        while (i < n1 && j < n2) {
            if (nums1[i] == nums2[j]) {
                // If both elements are equal, it's part of the intersection
                set.add(nums1[i]);
                i++;
                j++;
            } else if (nums1[i] < nums2[j]) {
                // Move pointer i if nums1[i] is smaller
                i++;
            } else {
                // Move pointer j if nums2[j] is smaller
                j++;
            }
        }

        //  Step 5: Convert the Set to an array (required return type)
        int[] result = new int[set.size()];
        int k = 0;

        for (int num : set) {
            result[k++] = num;
        }

        // Step 6: Return the result array
        return result;
    }
}


Approach 2:


class Solution {
    public int[] intersection(int[] nums1, int[] nums2) {
          Set<Integer> set1 = new HashSet<>();
        Set<Integer> resultSet = new HashSet<>();

        // Add all elements from nums1 into set1
        for (int num : nums1) {
            set1.add(num);
        }

        // Check if nums2 elements exist in set1
        for (int num : nums2) {
            if (set1.contains(num)) {
                resultSet.add(num);
            }
        }

        // Convert resultSet to int array
        int[] result = new int[resultSet.size()];
        int i = 0;
        for (int num : resultSet) {
            result[i++] = num;
        }

        return result;
    }
}

Comments

Post a Comment

Popular posts from this blog

Two Sum II - Input Array Is Sorted

 Given a 1-indexed array of integers numbers that is already sorted in non-decreasing order , find two numbers such that they add up to a specific target number. Let these two numbers be numbers[index1] and numbers[index2] where 1 <= index1 < index2 <= numbers.length. Return the indices of the two numbers, index1 and index2, added by one as an integer array [index1, index2] of length 2. The tests are generated such that there is exactly one solution. You may not use the same element twice. Your solution must use only constant extra space .   Example 1: Input: numbers = [2,7,11,15], target = 9 Output: [1,2] Explanation: The sum of 2 and 7 is 9. Therefore, index1 = 1, index2 = 2. We return [1, 2]. Example 2: Input: numbers = [2,3,4], target = 6 Output: [1,3] Explanation: The sum of 2 and 4 is 6. Therefore index1 = 1, index2 = 3. We return [1, 3]. Example 3: Input: numbers = [-1,0], target = -1 Output: [1,2] Explanation: The sum of -1 and 0 is -1. Therefore index1 = 1,...
Read more

Comparable Vs. Comparator in Java

  In Java , Comparable and Comparator both are interfaces used to sort objects. Comparable It defines  natural ordering  within a class. It is implemented  inside  the class being sorted. It uses the compareTo() method. It allows sorting  by one one . Comparable provides a  single sorting sequence . In other words, we can sort the collection on the basis of a single element such as id, name, and price. Comparable  affects the original class , i.e., the actual class is modified. Comparable is present in  java.lang  package. We can sort the list elements of Comparable type by  Collections.sort(List)  method. Only one compareTo() method can be implemented, restricting flexibility. Comparator It defines  custom sorting logic It is implemented  in a separate class  or using lambda expressions . It uses the compare() method. It allows sorting  by multiple criteria . The Comparator provides  multiple sorting...
Read more

Increasing Triplet Subsequence

 Given an integer array nums, return true if there exists a triple of indices (i, j, k) such that i < j < k and nums[i] < nums[j] < nums[k]. If no such indices exists, return false.   Example 1: Input: nums = [1,2,3,4,5] Output: true Explanation: Any triplet where i < j < k is valid. Example 2: Input: nums = [5,4,3,2,1] Output: false Explanation: No triplet exists. Example 3: Input: nums = [2,1,5,0,4,6] Output: true Explanation: The triplet (3, 4, 5) is valid because nums[3] == 0 < nums[4] == 4 < nums[5] == 6. Brute Force : Failed for some testcase class Solution {     public boolean increasingTriplet ( int [] nums ) {         int n = nums . length ;         int i = 0 ;         int j =i+ 1 ;         int k =j+ 1 ;         while (i <n && j<n && k<n)         {         if (nums...
Read more