C++之常用算法
for_each
transform
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
class Tranfor
{
public:
int operator()(int var)
{
return var;
}
};
class MyPrint
{
public:
void operator()(int var)
{
cout << var<<" " ;
}
};
void test()
{
vector<int>v;
for (int i = 0;i < 10;i++)
{
v.push_back(i);
}
vector<int>vTarget;//目标容器
vTarget.resize(v.size());//目标容器需要提前开辟空间
transform(v.begin(),v.end(),vTarget.begin(),Tranfor());
//遍历目标容器
for_each(vTarget.begin(), vTarget.end(),MyPrint());
cout << endl;
}
int main()
{
test();
system("pause");
return 0;
}
常用查找算法
find
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
#include<string>
//查找内置数据类型
void test()
{
vector<int>v;
for (int i = 0;i < 10;i++)
{
v.push_back(i);
}
vector<int>::iterator it = find(v.begin(),v.end(),5);
if (it == v.end())
{
cout << "没有找到" << endl;
}
else
{
cout << "找到了" << *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== 底层find知道该如何对比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;
};
void test2()
{
//定义容器
vector<Person>v1;
//创建数据（对象）
Person p1("aaa", 20);
Person p2("bbb", 30);
Person p3("ccc", 40);
Person p4("ddd", 50);
//将数据放入容器
v1.push_back(p1);
v1.push_back(p2);
v1.push_back(p3);
v1.push_back(p4);
//查到对象数据
vector<Person>::iterator it = find(v1.begin(), v1.end(), p2);
if (it == v1.end())
{
cout << "没有找到" << endl;
}
else
{
cout << "找到了 名字为：" << it->m_Name << "年龄为：" << it->m_Age << endl;
}
}
int main()
{
test2();
system("pause");
return 0;
}
find_if
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
#include<string>
//查找内置数据类型
class Greater
{
public:
bool operator()(int val)
{
return val > 5;
}
};
void test()
{
vector<int>v;
for (int i = 0;i < 10;i++)
{
v.push_back(i);
}
vector<int>::iterator it = find_if(v.begin(),v.end(), Greater());
if (it == v.end())
{
cout << "没有找到" << endl;
}
else
{
cout << "找到了" << *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;
}
string m_Name;
int m_Age;
};
class GreatAge
{
public:
bool operator()(Person&p)
{
return p.m_Age > 20;
}
};
void test2()
{
//定义容器
vector<Person>v1;
//创建数据（对象）
Person p1("aaa", 20);
Person p2("bbb", 30);
Person p3("ccc", 40);
Person p4("ddd", 50);
//将数据放入容器
v1.push_back(p1);
v1.push_back(p2);
v1.push_back(p3);
v1.push_back(p4);
//查到对象数据
vector<Person>::iterator it = find_if(v1.begin(), v1.end(), GreatAge());
if (it == v1.end())
{
cout << "没有找到" << endl;
}
else
{
cout << "找到了 名字为：" << it->m_Name << "年龄为：" << it->m_Age << endl;
}
}
int main()
{
test2();
system("pause");
return 0;
}
adjacent_find
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
#include<string>
void test()
{
vector<int>v;
v.push_back(9);
v.push_back(3);
v.push_back(4);
v.push_back(5);
v.push_back(5);
vector<int>::iterator it = adjacent_find(v.begin(),v.end());
if (it == v.end())
{
cout << "没有找到" << endl;
}
else
{
cout << "找到了" << *it << endl;
}
}
int main()
{
test();
system("pause");
return 0;
}
binary_search
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
#include<string>
void test()
{
vector<int>v;
for (int i = 0;i < 10;i++)
{
v.push_back(i);
}
//注意:容器必须是有序的序列
bool rat = binary_search(v.begin(), v.end(), 9);
if (rat == true)
{
cout << "找到了" << endl;
}
else
{
cout << "没有找到" << endl;
}
}
int main()
{
test();
system("pause");
return 0;
}
count
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
#include<string>
void test()
{
vector<int>v;
v.push_back(30);
v.push_back(50);
v.push_back(30);
v.push_back(20);
v.push_back(50);
int num = count(v.begin(), v.end(), 50);
cout << "找到元素50" << num << 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== 底层find知道该如何对比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;
};
void test2()
{
//定义容器
vector<Person>v1;
//创建数据（对象）
Person p1("aaa", 20);
Person p2("bbb", 30);
Person p3("ccc", 40);
Person p4("ddd", 50);
//将数据放入容器
v1.push_back(p1);
v1.push_back(p2);
v1.push_back(p3);
v1.push_back(p4);
//查到对象数据
Person p5("ddd", 50);
int num = count(v1.begin(), v1.end(), p5);
cout << "和ddd同岁的人" << num << endl;
}
int main()
{
test2();
system("pause");
return 0;
}
count_if
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
#include<string>
class Greater
{
public:
bool operator()(int val)
{
return val > 40;
}
};
void test()
{
vector<int>v;
v.push_back(30);
v.push_back(50);
v.push_back(30);
v.push_back(20);
v.push_back(50);
int num = count_if(v.begin(), v.end(), Greater());
cout << "找到大于40的个数" << num << 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;
}
string m_Name;
int m_Age;
};
class GreatAge
{
public:
bool operator()(Person& p)
{
return p.m_Age > 20;
}
};
void test2()
{
//定义容器
vector<Person>v1;
//创建数据（对象）
Person p1("aaa", 20);
Person p2("bbb", 30);
Person p3("ccc", 40);
Person p4("ddd", 50);
//将数据放入容器
v1.push_back(p1);
v1.push_back(p2);
v1.push_back(p3);
v1.push_back(p4);
int num = count_if(v1.begin(), v1.end(), GreatAge());
cout << "岁数大于20的个数" << num << endl;
}
int main()
{
test2();
system("pause");
return 0;
}