229. Majority Element II

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.

class Solution {
public:
    vector<int> majorityElement(vector<int>& nums) {
     
        
        if(nums.size()==0)
            return vector<int>();
        vector<int> res;
        if(nums.size()==1)
        {    
            res.push_back(nums[0]);
            return res;
        }
        int cnt1 = 0;
        int cnt2 = 0;
        int num1 = 0;
        int num2 = 0;
        
        cnt1 = 1;
        num1 = nums[0];
        for(int i=1; i<nums.size(); i++)
        {
            if(num1==nums[i])
            {
                cnt1++;
            }else if(num2==nums[i])
            {
                cnt2++;
            }else if(cnt1 == 0)
            {
                cnt1 = 1;
                num1 = nums[i];
            }else if(cnt2 == 0)
            {
                cnt2 = 1;
                num2 = nums[i];
            }else
            {
                cnt1--;
                cnt2--;
            }
            
        }
        cnt1 = 0;
        cnt2 = 0;
        for(int i=0; i<nums.size(); i++)
        {
            if(nums[i]==num1) cnt1++;
            else if(nums[i]==num2) cnt2++;
        }
        if(cnt1>nums.size()/3) res.push_back(num1);
        if(cnt2>nums.size()/3) res.push_back(num2);
        return res;
        
    }
};