查找算法

::: tips 查找算法 :::

• find_if(iterator beg, iterator end, _Pred);

  #include<iostream>
  using namespace std;
  #include<vector>
  #include<algorithm>
  #include<string>
  
  //常用查找算法：find_if
  
  //1. 查找内置数据类型
  class GreaterFive
  {
  public:
  	bool operator()(int val)
  	{
  		return val > 5;
  	}
  };
  
  void test01()
  {
  	vector<int>v;
  	for (int i = 0; i < 10; i++)
  	{
  		v.push_back(i);
  	}
  
  	//查找容器中是否有大于5的元素
  	vector<int>::iterator it = find_if(v.begin(), v.end(), GreaterFive());
  	if (it == v.end())
  	{
  		cout << "未找到大于5的元素！" << endl;
  	}
  	else
  	{
  		cout << "找到大于5的元素：" << *it << endl;
  	}
  }
  
  //2. 查找自定义数据类型（必须重载==）
  class Person
  {
  public:
  	Person(string name, int age)
  	{
  		this->m_Name = name;
  		this->m_Age = age;
  	}
  	//重载==使得底层find知道如何对比Person数据类型
  	bool operator==(const Person &p)
  	{
  		if (this->m_Name == p.m_Name&&this->m_Age == p.m_Age)
  		{
  			return true;
  		}
  		else
  		{
  			return false;
  		}
  	}
  
  	string m_Name;
  	int m_Age;
  };
  
  class Greater20
  {
  public:
  	bool operator()(Person &p)
  	{
  		return p.m_Age > 20;
  	}
  };
  
  void test02()
  {
  	vector<Person>v;
  
  	//创建数据
  	Person p1("aaa", 10);
  	Person p2("bbb", 20);
  	Person p3("ccc", 30);
  	Person p4("ddd", 40);
  
  	//放到容器中
  	v.push_back(p1);
  	v.push_back(p2);
  	v.push_back(p3);
  	v.push_back(p4);
  
  	//查找容器中是否有年龄大于20的人
  	vector<Person>::iterator it = find_if(v.begin(), v.end(), Greater20());
  	if (it == v.end())
  	{
  		cout << "未找到年龄大于20的人！" << endl;
  	}
  	else
  	{
  		cout << "找到年龄大于20的人！姓名：" << it->m_Name << "    年龄：" << it->m_Age << endl;
  	}
  }
  
  int main()
  {
  	test01();
  	test02();
  
  	system("pause");
  
  	return 0;
  }
  

• adjacent_find(iterator beg, iterator end);

  #include<iostream>
  using namespace std;
  #include<vector>
  #include<algorithm>
  #include<string>
  
  //常用查找算法：adjacent_find
  
  void test01()
  {
  	vector<int>v;
  
  	v.push_back(0);
  	v.push_back(2);
  	v.push_back(0);
  	v.push_back(3); 
  	v.push_back(1);
  	v.push_back(4);
  	v.push_back(3);
  	v.push_back(3);
  
  	//查找容器中是否有相邻重复元素
  	vector<int>::iterator it = adjacent_find(v.begin(), v.end());
  	if (it == v.end())
  	{
  		cout << "未找到相邻重复元素！" << endl;
  	}
  	else
  	{
  		cout << "找到相邻重复元素：" << *it << endl;
  	}
  }
  
  int main()
  {
  	test01();
  
  	system("pause");
  
  	return 0;
  }
  

• count_if(iterator beg, iterator end, _Pred);

  #include<iostream>
  using namespace std;
  #include<vector>
  #include<algorithm>
  #include<string>
  
  //常用查找算法：count_if
  
  //1. 统计内置数据类型
  class Greater20
  {
  public:
  	bool operator()(int val)
  	{
  		return val > 20;
  	}
  };
  
  void test01()
  {
  	vector<int>v;
  
  	v.push_back(10);
  	v.push_back(40);
  	v.push_back(30);
  	v.push_back(40);
  	v.push_back(20);
  	v.push_back(40);
  
  	//统计大于20的元素的个数
  	int num = count_if(v.begin(), v.end(), Greater20());
  	cout << "大于20的元素个数为：" << 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;
  };
  
  class AgeGreater20
  {
  public:
  	bool operator()(Person &p)
  	{
  		return p.m_Age > 20;
  	}
  };
  
  void test02()
  {
  	vector<Person>v;
  	
  	Person p1("刘备", 35);
  	Person p2("关羽", 35);
  	Person p3("张飞", 35);
  	Person p4("赵云", 30);
  	Person p5("曹操", 20);
  	
  	v.push_back(p1);
  	v.push_back(p2);
  	v.push_back(p3);
  	v.push_back(p4);
  	v.push_back(p5);
  	
  	//统计大于20岁的人员个数
  	int num = count_if(v.begin(), v.end(), AgeGreater20());
  		
  	cout << "年龄大于20岁的人员个数为：" << num << endl;
  }
  
  int main()
  {
  	test01();
  	test02();
  
  	system("pause");
  
  	return 0;
  }
  

  random_shuffle(iterator beg, iterator end);

#include <algorithm>
#include <vector>
#include <ctime>

class myPrint
{
public:
	void operator()(int val)
	{
		cout << val << " ";
	}
};

void test01()
{
	srand((unsigned int)time(NULL));
	vector<int> v;
	for(int i = 0 ; i < 10;i++)
	{
		v.push_back(i);
	}
	for_each(v.begin(), v.end(), myPrint());
	cout << endl;

	//打乱顺序
	random_shuffle(v.begin(), v.end());
	for_each(v.begin(), v.end(), myPrint());
	cout << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}

merge(iterator beg1, iterator end1, iterator beg2, iterator end2, iterator dest);

#include <algorithm>
#include <vector>

class myPrint
{
public:
	void operator()(int val)
	{
		cout << val << " ";
	}
};

void test01()
{
	vector<int> v1;
	vector<int> v2;
	for (int i = 0; i < 10 ; i++) 
    {
		v1.push_back(i);
		v2.push_back(i + 1);
	}

	vector<int> vtarget;
	//目标容器需要提前开辟空间
	vtarget.resize(v1.size() + v2.size());
	//合并  需要两个有序序列
	merge(v1.begin(), v1.end(), v2.begin(), v2.end(), vtarget.begin());
	for_each(vtarget.begin(), vtarget.end(), myPrint());
	cout << endl;
}

int main() {

	test01();

	system("pause");

	return 0;
}