169. Majority Element (Array)

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.

Moore voting algorithm--每找出两个不同的element，就成对删除即count--，最终剩下的一定就是所求的。时间复杂度：O(n)

class Solution {
public:
    int majorityElement(vector<int>& nums) {
        int count = 0;
        int preNum = nums[0];
        for(int i = 1; i < nums.size(); i++){
            if(nums[i]==preNum){
                count++;
            }
            else{
                if(count == 0){
                    preNum = nums[i];
                }
                else{
                    count--;
                }
            }
        }
        return preNum;
    }
};