229. Majority Element II

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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.
方法一：Language-Java Time-O(n) Space-O(1) RunTime-3ms

public class Solution {    public List<Integer> majorityElement(int[] nums) {        if(nums == null || nums.length == 0)        {            return new ArrayList<Integer>();        }        List<Integer> res = new ArrayList<Integer>();        int len = nums.length;        int number1 = nums[0];        int number2 = nums[0];        int count1 = 0;        int count2 = 0;        for(int i = 0; i < len; i ++)        {            //以下分支中每次只执行一个            if(nums[i] == number1)            {                count1 ++;            }else if(nums[i] == number2)            {                count2 ++;            }else if(count1 == 0)            {                number1 = nums[i];                count1 = 1;            }else if(count2 == 0)            {                number2 = nums[i];                count2 = 1;            }else            {                count1 --;                count2 --;            }        }        count1 = 0;        count2 = 0;        for(int i = 0; i < len; i ++)        {            if(nums[i] == number1)            {                count1 ++;            }else if(nums[i] == number2) //如果只有一个数就不会执行这里            {                count2 ++;            }        }        if(count1 > len/3 )        {            res.add(number1);        }        if(count2 > len/3 )        {            res.add(number2);        }        return res;    }}

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