Leetcode之Majortity Element II

题目：

Given an integer array of size n, find all elements that appear more than ⌊ n/3 ⌋ times.

Note: The algorithm should run in linear time and in O(1) space.

Example 1:

Input: [3,2,3]
Output: [3]

Example 2:

Input: [1,1,1,3,3,2,2,2]
Output: [1,2]

代码：

class Solution {
public:
    vector<int> majorityElement(vector<int>& nums) {
        vector<int> res;
        int a = 0, b = 0, cnt1 = 0, cnt2 = 0, n = nums.size();
        for (int num : nums) {
            if (num == a) ++cnt1;
            else if (num == b) ++cnt2;
            else if (cnt1 == 0) { a = num; cnt1 = 1; }
            else if (cnt2 == 0) { b = num; cnt2 = 1; }
            else { --cnt1; --cnt2; }
        }
        cnt1 = cnt2 = 0;
        for (int num : nums) {
            if (num == a) ++cnt1;
            else if (num == b) ++cnt2;
        }
        if (cnt1 > n / 3) res.push_back(a);
        if (cnt2 > n / 3) res.push_back(b);
        return res;
    }
};

想法：摩尔投票法

来源：CSDN

作者：一只荣

链接：https://blog.csdn.net/qq_35455503/article/details/104089102