229. Majority Element II

Posted 2020-08-11 Machelsky

Given an integer array of size n, find all elements that appear more than ⌊ n/3 ⌋ times. The algorithm should run in linear time and in O(1) space.

思路：边扫边存边判断。比较naive的做法。

public class Solution {
    public List<Integer> majorityElement(int[] nums) {
        List<Integer> check=new ArrayList<Integer>();
        if(nums.length==0)
        {
            return check;
        }
        Map<Integer,Integer> res=new HashMap<Integer,Integer>();
        for(int i=0;i<nums.length;i++)
        {
            if(!res.containsKey(nums[i]))
            {
                res.put(nums[i],1);
            }
            else
            {
                res.put(nums[i],res.get(nums[i])+1);
            }
            if(!check.contains(nums[i]))
            {
            if(res.get(nums[i])>(nums.length/3))
            {
                check.add(nums[i]);
            }
            }
        }
        return check;
        
    }
}