229. Majority Element II java solutions

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.

Hint:

1. How many majority elements could it possibly have?
2. Do you have a better hint? Suggest it!

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public class Solution {
    public List<Integer> majorityElement(int[] nums) {
        List<Integer> ans = new ArrayList<Integer>();
        if(nums.length <= 0) return ans;
        Arrays.sort(nums);
        int i = 0,len = nums.length,tmp = 0;
        while(i < len - len/3){
            if(nums[i] == nums[i+len/3]){
                tmp = nums[i];
                ans.add(tmp);
                i += len/3;
                while(i < len - len/3 && nums[i] == tmp)i++;
            }else i++;
        }
        return ans;
    }
}

解法二：

可用一个hashmap 来计算元素出现个数，但是超过space O(1) 的限制。

解法三：

https://discuss.leetcode.com/topic/32510/java-easy-version-to-understand/2 二刷在研究。