【C++】STL-常用算法-常用查找算法

0.前言

1.find

#include 
using namespace std;

// 常用查找算法 find
#include
#include

//查找 内置数据类型
void test01()
{
	vector<int>v;
	for (int i = 0; i < 10; i++)
	{
		v.push_back(i);
	}

	//查找 容器中 是否有 5 这个元素
	vector<int>::iterator it = find(v.begin(), v.end(), 5); // 返回迭代器类型 
	
	if (it == v.end())
	{
		cout << "没找到" << endl;
	}
	else
	{
		cout << "找到： " << *it << endl;
	}
}

//查找 自定义数据类型

class Person
{
public:
	Person(string name, int age)
	{
		this->m_Name = name;
		this->m_Age = age;
	}

	//重载 == 让底层find知道如何对比person数据类型
	bool operator==(const Person&p) //加const 防止修改数据
	{
		if (p.m_Name == this->m_Name && p.m_Age == this->m_Age)
		{
			return true;
		}
		else
		{
			return false;
		}
	}

	string m_Name;
	int m_Age;
};

void test02()
{
	//创建数据
	Person p1("a", 10);
	Person p2("b", 20);
	Person p3("c", 30);

	//放入容器中
	vector<Person>v;
	v.push_back(p1);
	v.push_back(p2);
	v.push_back(p3);

	Person p5("b", 20);

	vector<Person>::iterator it = find(v.begin(), v.end(), p5);

	if (it == v.end())
	{
		cout << "未找到" << endl;
	}
	else
	{
		cout << "找到： 姓名: " << it->m_Name << "  age:" << (*it).m_Age << endl;
	}
}

int main()
{
	test01();
	cout << "------------------------" << endl;
	test02();
	//cout << "------------------------" << endl << endl;
	//test03();

	//**************************************
	system("pause");
	return 0;
} 

2.find_if

#include 
using namespace std;

// 常用查找算法 find_if
#include


//1.查找内置数据类型

class Greater5
{
public:
	bool operator()(int val)
	{
		return val > 5;
	}
};

void test01()
{
	vector<int>v;

	for (int i = 0; i < 10; i++)
	{
		v.push_back(i);
	}

	vector<int>::iterator it = find_if(v.begin(), v.end(), Greater5());

	if (it == v.end())
	{
		cout << "no find" << endl;
	}
	else
	{
		cout << "find element: " << (*it) << endl;
	}
}

//2、查找自定义数据类型

class Person
{
public:
	Person(string name, int age)
	{
		this->m_Name = name;
		this->m_Age = age;
	}

	string m_Name;
	int m_Age;
};

//方式一 利用仿函数
//class greater_Age20
//{
//public:
//	bool operator()(const Person& p)
//	{
//		return p.m_Age > 20;
//	}
//};

//方式二 利用普通函数
bool greater_Age20(const Person& p)
{
	return p.m_Age > 20;
}


void test02()
{
	//创建对象
	Person p1("a", 10);
	Person p2("b", 20);
	Person p3("c", 30);
	
	vector<Person>v;
	v.push_back(p1);
	v.push_back(p2);
	v.push_back(p3);

	//查找年龄大于20的人
	vector<Person>::iterator it = find_if(v.begin(), v.end(), greater_Age20);

	if (it == v.end())
	{
		cout << "no find" << endl;
	}
	else
	{
		cout << "find the element: name:" << it->m_Name << " age:" << it->m_Age << endl;
	}
}

int main()
{
	test01();
	cout << "------------------------" << endl;
	test02();
	//cout << "------------------------" << endl << endl;
	//test03();

	//**************************************
	system("pause");
	return 0;
} 

3.adjacent_find

#include 
using namespace std;

// 常用查找算法 adjacent_find
#include
#include

void test01()
{
	//创建对象
	vector<int>v;
	v.push_back(1);
	v.push_back(2);
	v.push_back(1);
	v.push_back(3);
	v.push_back(4);
	v.push_back(3);
	v.push_back(3);

	vector<int>::iterator pos = adjacent_find(v.begin(), v.end());

	if (pos == v.end())
	{
		cout << "no find adjacent duplcate elements " << endl;
	}
	else
	{
		cout << "find adjacent duplcate elements: " << *pos << endl;
	}
}

int main()
{
	test01();
	cout << "------------------------" << endl;
	//test02();
	//cout << "------------------------" << endl << endl;
	//test03();

	//**************************************
	system("pause");
	return 0;
} 

4.binary_search

#include 
using namespace std;

// 常用查找算法 binary_search 二分查找
#include
#include

void test01()
{
	vector<int>v;
	for (int i = 0; i < 10; i++)
	{
		v.push_back(i);
	}

	//v.push_back(2);  如果是无序序列，结果未知！
	//查找容器中是否有9元素
	//注意：容器必须是有序的序列（从小到大）
	bool ret = binary_search(v.begin(), v.end(),9);

	if (ret)
	{
		cout << "find point element" << endl;
	}
	else
	{
		cout << "no find" << endl;
	}
}

int main()
{
	test01();
	cout << "------------------------" << endl;
	//test02();
	//cout << "------------------------" << endl << endl;
	//test03();

	//**************************************
	system("pause");
	return 0;
} 

5.count

#include 
using namespace std;

// 常用查找算法 count
#include
#include

//1.统计内置数据类型
void test01()
{
	vector<int>v;
	v.push_back(1);
	v.push_back(4);
	v.push_back(1);
	v.push_back(3);

	int num = count(v.begin(), v.end(), 1);
	
	cout << "the nmber of point element: " << num << endl;
}

//2.统计自定义数据类型
class Person
{
public:
	Person(string name, int age)
	{
		this->m_Name = name;
		this->m_Age = age;
	}

	bool operator==(const Person& p)
	{
		if (p.m_Age == this->m_Age)
		{
			return true;
		}
		else
		{
			return false;
		}
	}

	string m_Name;
	int m_Age;
};
void test02()
{
	//创建对象
	Person p1("刘备", 35);
	Person p2("薇恩", 24);
	Person p3("皮城", 35);
	Person p4("光辉", 40);

	vector<Person>v;
	v.push_back(p1);
	v.push_back(p2);
	v.push_back(p3);
	v.push_back(p4);

	Person p5("卡米尔", 35);

	int num = count(v.begin(), v.end(), p5);
	 
	cout << "跟卡米尔同岁的人有多少个: " << num << endl;
}

int main()
{
	test01();
	cout << "------------------------" << endl;
	//test02();
	//cout << "------------------------" << endl << endl;
	//test03();

	//**************************************
	system("pause");
	return 0;
} 

6.count_if

#include 
using namespace std;


// 常用查找算法 count_if
#include
#include

//1、统计内置数据类型

//利用仿函数
class Greater3
{
public:
	bool operator()(int val)
	{
		return val > 3;
	}
};

void test01()
{
	vector<int>v;
	v.push_back(1);
	v.push_back(6);
	v.push_back(3);
	v.push_back(2);
	v.push_back(4);
	v.push_back(3);

	int num = count_if(v.begin(), v.end(), Greater3());

	cout << "the number of element greater than 3 :  " << num << endl;
}

//2、统计自定义数据类型

class Person
{
public:
	Person(string name, int age)
	{
		this->m_Name = name;
		this->m_Age = age;
	}

	string m_Name;
	int m_Age;
};

//利用普通函数
bool age_Greater35(const Person& p)
{
	if (p.m_Age > 35)
	{
		return true;
	}
	else
	{
		return false;
	}
}

void test02()
{

	//创建对象
	Person p1("刘备", 35);
	Person p2("薇恩", 24);
	Person p3("皮城", 35);
	Person p4("光辉", 40);
	
	vector<Person>v;
	v.push_back(p1);
	v.push_back(p2);
	v.push_back(p3);
	v.push_back(p4);

	//统计岁数大于35的人物的个数
	int num = count_if(v.begin(), v.end(), age_Greater35);

	cout << "the number of character whose age greater than 35 :" << num << endl;
}

int main()
{
	test01();
	cout << "------------------------" << endl;
	test02();
	//cout << "------------------------" << endl << endl;
	//test03();

	//**************************************
	system("pause");
	return 0;
}