LeetCode: 169. Majority Element

题目描述

Given an array of size n, find the majority element. The majority element is the element that appears more than ⌊ n/2 ⌋ times.

You may assume that the array is non-empty and the majority element always exist in the array.

Example 1:

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

Example 2:

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

解题思路

由于主元素(Majority Element) 的定义是出现次数超过半数的元素，且一定存在。因此，如果相邻元素不相等，直接丢弃，否则记录下它出现的次数, 留待和后面的比较。最后剩下的元素就主元素。

AC 代码

class Solution {
public:
    int majorityElement(vector<int>& nums) {
        int lastNum = INT_MIN;
        int cnt = 0;
        for(size_t i = 0; i < nums.size(); ++i)
        {
            if(cnt == 0 || lastNum == nums[i])
            {
                ++cnt;
                lastNum = nums[i];
            }
            else
            {
                --cnt;
            }
        }

        return lastNum;
    }
};