C++进阶STL-常用的排序算法

merge：将两个容器的元素融合成一个容器中，并进行排序

• merge(v1.begin(), v1.end(), v2.begin(), v2.end(), v3.begin(), Compare());
• 进行操作前，两个容器的排序规则需要一样，第三个容器的排序规则也需要相同
• 默认是进行从小到大，如需要自己定义规则
• v1和v2可以是支持随机访问的，也可以是不支持随机访问的容器，如list容器（例2）
  

例1：

#include "stdafx.h"
#include <iostream>
#include <algorithm>
#include <vector>
#include <functional>
#include <time.h>
using namespace std;

struct Print
{
	void operator()(int n)
	{
		cout << " " << n;
	}
	
};

struct Compare
{
	bool operator()(int n,int m)
	{
		return n>m;
	}

};

int main()
{

	vector<int> v1,v2;
	srand((unsigned int) time(NULL));
	
	for (int i = 0; i < 5; i++) //构造v1
	{
		v1.push_back(rand() % 10);
	}
	

	for (int i = 0; i < 10; i++)//构造v2
	{
		v2.push_back(rand() % 10);
	}

	for_each(v1.begin(), v1.end(), Print()); cout << endl; //打印原始元素
	for_each(v2.begin(), v2.end(), Print()); cout << endl;

	sort(v1.begin(), v1.end(), Compare());      //按从大到小顺序排列（默认从小到大）
	sort(v2.begin(), v2.end(), Compare());
	cout << "-----------------" << endl;
	
	for_each(v1.begin(), v1.end(), Print()); cout << endl; //排序之后再打印
	for_each(v2.begin(), v2.end(), Print()); cout << endl;
	cout << "-----------------" << endl;

	vector<int> v3;
	v3.resize(v1.size() + v2.size());//构造v3

	merge(v1.begin(), v1.end(), v2.begin(), v2.end(), v3.begin(), Compare()); //将v1 v2 融合排序 之后 交给v3
	for_each(v3.begin(), v3.end(), Print()); cout << endl;

    return 0;
}

结果：

---

例2：

#include "stdafx.h"
#include <iostream>
#include <algorithm>
#include <vector>
#include <functional>
#include <time.h>
#include <list>
using namespace std;

struct Print
{
	void operator()(int n)
	{
		cout << " " << n;
	}
	
};

struct Compare
{
	bool operator()(int n,int m)
	{
		return n>m;
	}

};

int main()
{

	vector<int> v1;
	list<int>l2;
	srand((unsigned int) time(NULL));
	
	for (int i = 0; i < 5; i++)
	{
		v1.push_back(rand() % 10);
	}                                                             //构造一个vector，一个list ，输出结果
	
	for (int i = 0; i < 10; i++)
	{
		l2.push_back(rand() % 10);
	}
	
	for_each(v1.begin(), v1.end(), Print()); cout << " --->   vector container"<<endl;
	for_each(l2.begin(), l2.end(), Print()); cout <<"  --->   list container"<< endl;
	
/*---------------------------------------------------------------------------------------------------*/

	sort(v1.begin(), v1.end(), Compare());
	l2.sort(Compare());
                                                                   //进行排序，再输出
	cout << "-----------------" << endl;
	for_each(v1.begin(), v1.end(), Print()); cout << endl;
	for_each(l2.begin(), l2.end(), Print()); cout << endl;
	
/*---------------------------------------------------------------------------------------------------*/

	cout << "-----------------" << endl;
	vector<int> v3;
	v3.resize(v1.size() + l2.size());                                 
                                                                        //进行排序融合
	merge(v1.begin(), v1.end(), l2.begin(), l2.end(), v3.begin(), Compare());
	for_each(v3.begin(), v3.end(), Print()); cout << endl;

    return 0;
}

结果：

---

sort：排序

• sort（v1.begin()，v1.end()，Comapre()）
  上面案列有用到

---

reverse：倒序

• reverse(v1.begin()，v1.end())：不一定是从开始到结束，也可以是中间的区域

#include "stdafx.h"
#include <iostream>
#include <vector>
#include <functional>
#include <algorithm>

using namespace std;

class Person
{
public:
	Person(int age, int id) :m_age(age), m_id(id)
	{
	}
	void Print()
	{
		cout << " age: " << m_age <<"     id:" << m_id << endl;
	}

	int m_age;
	int m_id;
};

int main()
{
	vector <Person> v;
	Person p1(10, 10) ;
	Person p2(20, 20) ;
	Person p3(30, 30) ;
	Person p4(40, 40);
	v.push_back(p1);
	v.push_back(p2);
	v.push_back(p3);
	v.push_back(p4);

	for_each(v.begin(), v.end(), mem_fun_ref(&Person::Print));
	cout << "----------------------------" << endl;

	reverse(v.begin(), v.end()-1);
	for_each(v.begin(), v.end(), mem_fun_ref(&Person::Print));
   return 0;
}

结果：只反转了前三个

---

random_shuffle：打乱顺序，洗牌

• random_shuffle( v1.begin()，v1.end())

#include "stdafx.h"
#include <iostream>
#include <vector>
#include <algorithm>
#include <time.h>

using namespace std;

class Person
{
public:
	Person(int age, int id) :m_age(age), m_id(id)
	{
	}

	int m_age;
	int m_id;
};


struct Print
{
	void operator()(const Person&p1)
	{
		cout << p1.m_age << " ";
	}
};

int main()
{
	vector<Person> v1;
	Person p1(1, 1), p2(2, 2), p3(3, 3), p4(4, 4),p5(5,5);
	srand((unsigned int)time(NULL));

	v1.push_back(p1);
	v1.push_back(p2);
	v1.push_back(p3);
	v1.push_back(p4);
	v1.push_back(p4);
	v1.push_back(p5);


	for_each(v1.begin(), v1.end(), Print()); cout << endl;
	cout << "-------------" << endl;

	random_shuffle(v1.begin(), v1.end());
	for_each(v1.begin(), v1.end(), Print()); cout << endl;

    return 0;
}

结果：