【C++】STL-常用算法-常用查找算法

0.前言

1.find

#include <iostream>
using namespace std;// 常用查找算法 find
#include<vector>
#include<algorithm>//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 <iostream>
using namespace std;// 常用查找算法 find_if
#include<vector>//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 <iostream>
using namespace std;// 常用查找算法 adjacent_find
#include<vector>
#include<algorithm>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 <iostream>
using namespace std;// 常用查找算法 binary_search 二分查找
#include<vector>
#include<algorithm>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 <iostream>
using namespace std;// 常用查找算法 count
#include<vector>
#include<algorithm>//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 <iostream>
using namespace std;// 常用查找算法 count_if
#include<vector>
#include<algorithm>//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;
}