Majority Element

最新推荐文章于 2022-04-16 14:23:13 发布

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本文提供了三种不同的算法来解决寻找数组中多数元素的问题：通过排序、使用关联容器和Boyer-Moore投票算法。多数元素是指在大小为n的数组中出现次数超过n/2的元素。

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.

#include<iostream>
#include<vector>
#include<algorithm>
#include<map>
using namespace std;
//先排序
int majorityElement(vector<int> &num) {
	sort(num.begin(),num.end());
	int mid = num.size()/2;
	return num[mid];
}
//利用关联容器
int majorityElement(vector<int> &num) {
	if(num.size()==1)
		return num[0];
	map<int,int> Mapcount;
	for (int i =0;i!=num.size();++i)
	{
		if (Mapcount.count(num[i]))
		{
			++Mapcount[num[i]];
			if (Mapcount[num[i]]>num.size()/2)
				return num[i];
		}
		else
			Mapcount.insert(make_pair(num[i],1));
	}
}
//将重复点与非重复点成对计算
int majorityElement(vector<int> &num) {
	int nTimes = 0;
	int candidate = 0;
	for(int i = 0; i < num.size(); i ++){
		if(nTimes == 0){
			candidate = num[i];
			nTimes = 1;
		}
		else{
			if(candidate == num[i])
				nTimes ++;
			else
				nTimes --;
		}
	}
	return candidate;
}