Leetcode-- Majority Elemeny

Majority Element

原题：

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.

解题思路：刚开始的想法是直接对已有数组进行排序，但是这样做会改变原有数组，而且时间复杂度为O(n*logn)。具体代码如下：

class Solution {public:    int majorityElement(vector<int> &num) {        sort(num.begin(),num.end());        return num[num.size()/2];    }};

还有一种做法就是遍历整个数组，设置一个计数器，令第一个元素为待选元素，当下一元素和待选元素相同时，就++，不同时就--。若计数器为零，则更换待选元素。具体代码如下：

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