leetcode 229: Majority Element

Extended from Majority Element. Now there are at most two majority element, so I need four variables to implement the moore voting algorithm.

class Solution {
public:
    vector<int> majorityElement(vector<int>& nums) {
        int res1,count1,res2,count2;
        vector<int> res;
        int n=nums.size();
        if(n==0)
            return res;
        res1=nums[0];
        count1=1;
        count2=0;
        for(int i=1;i<n;i++)
        {
            if(res1==nums[i])//must judge before count1==0 and count2==0
                count1++;
            else if(res2==nums[i])//must judge before count1==0 and count2==0
                count2++;
            else if(count1==0)
            {
                res1=nums[i];
                count1++;
            }
            else if(count2==0)
            {
                res2=nums[i];
                count2++;
            }
            else
            {
                count1--;
                count2--;
            }
        }
        count1=count2=0;
        for(int i=0;i<n;i++)//count the two numbers again because there are some corner cases
        {
            if(nums[i]==res1)
                count1++;
            else if(nums[i]==res2)
                count2++;
        }
        if(count1>n/3)
            res.push_back(res1);
        if(count2>n/3)
            res.push_back(res2);
        return res;
    }
};