算法面试题-leetcode学习之旅（一）

问题描述

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.

解决思路：

推荐算法：

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)

java实现：

public class Solution {  
    public int majorityElement(int[] nums) {  
        //0627 
        //Moore Voting 
        int n = nums.length;  

        int candidate = 0;  
        int times = 0;  
        for(int i = 0; i < n; i++){  
            if(times == 0) candidate = nums[i];  
            if(nums[i] != candidate){  
                times--;  
            } else{  
                times++;  
            }  
        }  
        return candidate;  
        //0631 
    }  
}  

c实现：

class Solution {
public:
    int majorityElement(vector<int> &num) {

        int elem = 0;
        int count = 0;

        for(int i = 0; i < num.size(); i++)  {

            if(count == 0)  {
                elem = num[i];
                count = 1;
            }
            else    {
                if(elem == num[i])
                    count++;
                else
                    count--;
            }

        }
        return elem;
    }
　　};