方法1 (简单方法)

方法2 (使用归并排序)

方法3 (使用哈希)

#include<iostream>
#include<algorithm>
#include<map>
#include<list>

void calculateUnion(const std::list<int>& list1, const std::list<int>& list2, std::list<int>& outputResult)
{
	std::map< int, bool> tmp;

	for (auto iter : list1)
	{
		if (tmp.find(iter) == tmp.end())
			tmp.insert(std::make_pair(iter, true));
	}

	for (auto iter : list2)
	{
		if (tmp.find(iter) == tmp.end())
			tmp.insert(std::make_pair(iter, true));
	}

	//convert map to list
	for (auto iter : tmp)
	{
		if (iter.second)
			outputResult.push_back(iter.first);
	}

}

void calculateIntersection(const std::list<int>& list1, const std::list<int>& list2, std::list<int>& outputResult)
{
	std::map< int, bool> tmp;

	for (auto iter : list1)
	{
		tmp.insert(std::make_pair(iter, false));
	}

	for (auto iter : list2)
	{
		if (tmp.find(iter) != tmp.end())
			outputResult.push_back(iter);
	}
}


int main()
{
	//list1: 10->15->4->20
	//list2:  8->4->2->10
	std::list< int> list1, list2, result;
	list1.push_back(10);
	list1.push_back(15);
	list1.push_back(4);
	list1.push_back(20);

	list2.push_back(8);
	list2.push_back(4);
	list2.push_back(2);
	list2.push_back(10);

	calculateUnion(list1, list2, result);
	std::cout << "union result: \n";
	std::for_each(result.begin(), result.end(), [](const int& value){
		std::cout << value << " ";
	});

	result.clear();
	calculateIntersection(list1, list2, result);
	std::cout << "\nintersection result: \n";
	std::for_each(result.begin(), result.end(), [](const int& value){
		std::cout << value << " ";
	});
	std::cout << std::endl;

	return 0;
}

哈希(4) - 求两个链表的交集(intersection)以及并集(union)

原文：http://blog.csdn.net/shltsh/article/details/46484673