LeetCode40|有序数组中的单一元素

输入: [1,1,2,3,3,4,4,8,8]
输出: 2

import java.util.HashMap;

public class SingleNonDuplicateTest {
    public static void main(String[] args) {
        int [] array={1,1,2,3,3,4,4,8,8};
        int num = singleNonDuplicate(array);
        System.out.println("num = " + num);
    }

    public static  int singleNonDuplicate(int[] nums) {
        if (nums == null || nums.length == 0) {
            return -1;
        }
        int length = nums.length;
        HashMap<Integer, Integer> hashMap=new HashMap<>(length);
        for (Integer num:nums
             ) {
          hashMap.put(num,  hashMap.getOrDefault(num,0)+1);
        }
        return hashMap.entrySet().stream().filter(x -> x.getValue() == 1).findFirst().get().getKey();
    }
}