【数组】229. 求众数 II （摩尔投票法）

 

 解答：摩尔投票法

class Solution {
    public List<Integer> majorityElement(int[] nums) {
        List<Integer> res = new ArrayList<>();
        if(nums.length == 0) return res;

        int cand1 = nums[0],cand2 = nums[0],cnt1 = 0,cnt2 = 0;
        for(int i = 0;i<nums.length;i++){
            if(cand1 == nums[i]){
                cnt1++;
                continue;
            }
            if(cand2 == nums[i]){
                cnt2++;
                continue;
            }
            if(cnt1 == 0){
                cand1 = nums[i];
                cnt1++;
                continue;
            }
            if(cnt2 == 0){
                cand2 = nums[i];
                cnt2++;
                continue;
            }

            cnt1--;
            cnt2--;
        }
        int count1 = 0, count2 = 0;
        for(int num:nums){
            if(cand1 == num){
                count1++;
            }
            else if(cand2 == num){
                count2++;
            }
        }
        if(count1>nums.length/3){
            res.add(cand1);
        }
        if(count2>nums.length/3){
            res.add(cand2);
        }

        return res;
        
    }
}