645.set-mismatch.java

/*
 * @lc app=leetcode id=645 lang=java
 *
 * [645] Set Mismatch
 *
 * https://leetcode.com/problems/set-mismatch/description/
 *
 * algorithms
 * Easy (40.54%)
 * Likes:    421
 * Dislikes: 233
 * Total Accepted:    49K
 * Total Submissions: 120.1K
 * Testcase Example:  '[1,2,2,4]'
 *
 *
 * The set S originally contains numbers from 1 to n. But unfortunately, due to
 * the data error, one of the numbers in the set got duplicated to another
 * number in the set, which results in repetition of one number and loss of
 * another number.
 *
 *
 *
 * Given an array nums representing the data status of this set after the
 * error. Your task is to firstly find the number occurs twice and then find
 * the number that is missing. Return them in the form of an array.
 *
 *
 *
 * Example 1:
 *
 * Input: nums = [1,2,2,4]
 * Output: [2,3]
 *
 *
 *
 * Note:
 *
 * The given array size will in the range [2, 10000].
 * The given array's numbers won't have any order.
 *
 *
 */
class Solution {
  public int[] findErrorNums(int[] nums) {
    Set<Integer> set = new HashSet<>();
    int duplicate = 0;
    int miss = 0;

    for (int i = 0; i < nums.length; i++) {
      if (set.contains(nums[i])) {
        duplicate = nums[i];
      }
      set.add(nums[i]);
      miss = miss ^ (i + 1) ^ nums[i];
    }

     return new int[] {duplicate, miss ^ duplicate};
  }
}