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FindNumberWhichAppearsOnce.java
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FindNumberWhichAppearsOnce.java
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package by.andd3dfx.numeric;
import java.util.HashSet;
/**
* <pre>
* <a href="https://leetcode.com/problems/single-number/">Task description</a>
*
* Given a non-empty array of integers nums, every element appears twice except for one. Find that single one.
* You must implement a solution with a linear runtime complexity and use only constant extra space.
*
* Example 1:
* Input: nums = [2,2,1]
* Output: 1
*
* Example 2:
* Input: nums = [4,1,2,1,2]
* Output: 4
*
* Example 3:
* Input: nums = [1]
* Output: 1
* </pre>
*
* @see <a href="https://youtu.be/dNB8tOvx5Gk">Video solution</a>
*/
public class FindNumberWhichAppearsOnce {
public static int findSubOptimal(int[] numbers) {
var set = new HashSet<Integer>();
for (var number : numbers) {
if (!set.add(number)) {
set.remove(number);
}
}
return set.toArray(new Integer[0])[0];
}
public static int find(int[] numbers) {
int result = 0;
for (var number : numbers) {
result ^= number; // use fact that: ((X xor Y) xor Y) == X
}
return result;
}
}