169. Majority Element

题目：
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.
题解：

这道题有多种算法。一种是Moore voting 的算法做的。基本思想是这样子的：每次找出一对不同的数字并排除掉，不断的进行这样的操作，最后留下来的数字就是我们要的Majority Element。因为题干已经告诉了我们Majority Element是一定存在的。还有一种分治算法，就是以下解题所采用的方法：

class Solution {
public:
int majorityElement(vector<int>& nums)  {
if(nums.size() == 1)
return nums[0];

int size = nums.size();
int left,right;
vector <int> array1,array2;
for(int i = 0; i < size/2; i++) {
array1.push_back(nums[i]);
}
for(int i = size/2; i < size; i++) {
array2.push_back(nums[i]);
}
left = majorityElement(array1);
right = majorityElement(array2);

if(right == left)
return right;
int x = 0;
int y = 0;
for(int i = 0; i < size; i++) {
if(nums[i] == left)
x++;

if(nums[i] == right)
y++;
}
if(x > y)
return left;
else
return right;

}
};