Is Find the XOR of Numbers Which Appear Twice easy or hard?

The problem is classified as Easy because it relies on basic array traversal, duplicate detection, and the XOR operator. Once you recognize that the result should include only numbers that appear exactly twice, the implementation becomes straightforward.

Find the XOR of Numbers Which Appear Twice Python/Java solution

In Python or Java, iterate through the array while storing seen values in a set or boolean array. When a value appears for the second time, XOR it with the result variable. This implementation runs in O(n) time and requires minimal extra code.

How to solve Find the XOR of Numbers Which Appear Twice in O(n)?

Iterate through the array while tracking whether each number has appeared before. With a boolean array or hash set, detect the second occurrence and XOR the value into the result. Each element is processed once, producing an O(n) time algorithm.

What is the best approach for Find the XOR of Numbers Which Appear Twice?

The most efficient approach uses a boolean array to track whether a number has been seen before. When the same number appears the second time, XOR it with the running result. This processes the array in O(n) time and uses constant extra space because the tracking array size is fixed.

Is Find the XOR of Numbers Which Appear Twice asked at Google/Amazon/Meta?

Problems involving duplicate detection, XOR operations, and hash table counting appear frequently in coding interviews at companies like Amazon, Google, and Meta. This problem tests understanding of arrays, hash maps, and basic bit manipulation patterns.

What data structure is used in Find the XOR of Numbers Which Appear Twice?

The common data structures are a hash map for frequency counting or a boolean array for appearance tracking. The boolean array approach is more memory efficient when the input values fall within a small known range.

What is the time complexity of Find the XOR of Numbers Which Appear Twice?

Both common solutions run in O(n) time because the array is scanned once. A hash map frequency count uses O(n) space, while a boolean tracking array reduces space to O(1) when the value range is bounded.

3158. Find the XOR of Numbers Which Appear Twice - Practice Online

You are given an array nums, where each number in the array appears either once or twice.

Return the bitwise XOR of all the numbers that appear twice in the array, or 0 if no number appears twice.

Example 1:

Input: nums = [1,2,1,3]

Output: 1

Explanation:

The only number that appears twice in nums is 1.

Example 2:

Input: nums = [1,2,3]

Output: 0

Explanation:

No number appears twice in nums.

Example 3:

Input: nums = [1,2,2,1]

Output: 3

Explanation:

Numbers 1 and 2 appeared twice. 1 XOR 2 == 3.

Constraints:

1 <= nums.length <= 50
1 <= nums[i] <= 50
Each number in nums appears either once or twice.