leetcode讲解--961. N-Repeated Element in Size 2N Array

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

题目地址

讲解

这个题目很简单，只要扫描一遍数组，遇到一个数出现两次，就找到了这个数。

Java代码

class Solution {
    public int repeatedNTimes(int[] A) {
        Map<Integer, Integer> map = new HashMap<>();
        for(int x:A){
            Integer count = map.get(x);
            if(count==null){
                map.put(x, 1);
            }else{
                return x;
            }
        }
        return 0;
    }
}