Majority Element

Given an array of size n, find the majority element. The majority element is the element that appears more than ⌊ n/2 ⌋ times.

You may assume that the array is non-empty and the majority element always exist in the array.

 

第一种方法:

存到hashmap中，然后找出现次数多于一半的。

public class Solution {
    public int majorityElement(int[] num) {
        HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
        for(int n : num){
            if(map.containsKey(n)) map.put(n, map.get(n) + 1);
            else map.put(n, 1);
        }
        for(int i : map.keySet()){
            if(map.get(i) > num.length / 2) return i;
        }
        return -1;
    }
}