LeetCode 3158: Find the XOR of Numbers Which Appear Twice Solution

Master LeetCode problem 3158 (Find the XOR of Numbers Which Appear Twice), a easy challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

3158. Find the XOR of Numbers Which Appear Twice

Easy

Array Hash Table Bit Manipulation

Problem Explanation

Explanation:

To find the XOR of numbers which appear twice in the given array, we can utilize the properties of XOR operation. XOR of a number with itself results in 0. So, if a number appears twice in the array, XORing it with 0 will cancel out the effect of that number and leave us with 0. Therefore, by XORing all numbers in the array and considering only the numbers that appear twice, we can obtain the desired result.

Algorithm:

Initialize a variable result to store the final XOR value.
Initialize a set seenTwice to keep track of numbers appearing twice.
Iterate through the input array nums.
If a number is already present in seenTwice, XOR it with result.
If not present, add it to seenTwice.
Finally, return result.

Time Complexity: O(n), where n is the number of elements in the input array. Space Complexity: O(n) due to the set seenTwice.

Solution Code

import java.util.HashSet;
import java.util.Set;

class Solution {
    public int findNumbersAppearedTwice(int[] nums) {
        int result = 0;
        Set<Integer> seenTwice = new HashSet<>();
        
        for (int num : nums) {
            if (seenTwice.contains(num)) {
                result ^= num;
            } else {
                seenTwice.add(num);
            }
        }
        
        return result;
    }
}

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