LeetCode-in-Java

961. N-Repeated Element in Size 2N Array

Easy

You are given an integer array nums with the following properties:

• nums.length == 2 * n.
• nums contains n + 1 unique elements.
• Exactly one element of nums is repeated n times.

Return the element that is repeated n times.

Example 1:

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

Output: 3

Example 2:

Input: nums = [2,1,2,5,3,2]

Output: 2

Example 3:

Input: nums = [5,1,5,2,5,3,5,4]

Output: 5

Constraints:

• 2 <= n <= 5000
• nums.length == 2 * n
• 0 <= nums[i] <= 104
• nums contains n + 1 unique elements and one of them is repeated exactly n times.

Solution

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

public class Solution {
    public int repeatedNTimes(int[] nums) {
        Set<Integer> set = new HashSet<>();
        for (int num : nums) {
            if (!set.add(num)) {
                return num;
            }
        }
        return -1;
    }
}

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