LeetCode21|主要元素

输入：[1,2,5,9,5,9,5,5,5]
输出：5

 
import java.util.HashMap;
import java.util.Map;

public class MajorityElementTest {
    public static void main(String[] args) {
        int[] array = {1, 2, 5, 9, 5, 9, 5, 5, 5};
        int majorityElement = majorityElement(array);
        System.out.println("majorityElement = " + majorityElement);
    }

    public static int majorityElement(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
        ) {
            if (hashMap.containsKey(num)) {
                hashMap.put(num, hashMap.get(num) + 1);
            } else {
                hashMap.put(num, 1);
            }
        }
        return hashMap.entrySet().stream().filter(entry -> entry.getValue() > length / 2).findFirst().map(Map.Entry::getKey).orElse(-1);
    }
}