Leetcode 961. N-Repeated Element in Size 2N Array

Posted 2022-11-29 逆風的薔薇

题目

In a array A of size 2N, there are N+1 unique elements, and exactly one of these elements is repeated N times.

Return the element repeated N times.

 

Example 1:

Input: [1,2,3,3]
Output: 3

Example 2:

Input: [2,1,2,5,3,2]
Output: 2

Example 3:

Input: [5,1,5,2,5,3,5,4]
Output: 5

Note:

1. 4 <= A.length <= 10000
2. 0 <= A[i] < 10000
3. A.length is even

分析

2N个数，N+1 个唯一的数字，其中一个重复N次，只需找到出现两次的数字即可。

代码

class Solution 
    public int repeatedNTimes(int[] A) 
        Set<Integer> set = new HashSet<>();
        for (int x : A) 
            if (set.contains(x)) 
                return x;
            
            set.add(x);
        
        throw null;