C++,stl，常用遍历查找算法

目录​​​​​​​

1.常用遍历算法

for_each

transform

2.常用查找算法

find 

find_if 

adjacent_find

binary_search

count

count_if

---

1.常用遍历算法

for_each

#include
using namespace std;

void print(int v)
{
	cout << v << ' ';
}

class print2
{
public:
	void operator()(int v)
	{
		cout << v << ' ';
	}
};

int main()
{
	vector v;
	v.push_back(1);
	v.push_back(1);
	v.push_back(0);
	v.push_back(0);
	v.push_back(1);
	
	for_each(v.begin(),v.end(),print);
	cout << endl;
	
	//仿函数
	for_each(v.begin(),v.end(),print2());
	return 0;
}

 

transform

必须提前开辟空间 

#include
using namespace std;

class trans
{
public:
	int operator()(int v)
	{
		return v + 200;
	}
};

class print
{
public:
	void operator()(int v)
	{
		cout << v << ' ';
	}
};

int main()
{
	vector v;
	v.push_back(1);
	v.push_back(1);
	v.push_back(0);
	v.push_back(0);
	v.push_back(1);
	
	vector v1;
	v1.resize(v.size());
	transform(v.begin(),v.end(),v1.begin(),trans());
	
	for_each(v1.begin(),v1.end(),print());
}

 

2.常用查找算法

find 

#include
using namespace std;

int main()
{
	vector v;
	v.push_back(4);
	v.push_back(5);
	v.push_back(2);
	v.push_back(8);
	v.push_back(1);
	
	vector::iterator it;
	it = find(v.begin(),v.end(),8);
	if(it != v.end()) cout << "找到了" << endl;
}

 

自定义数据类型 

#include
using namespace std;

class person
{
public:
	person(string name,int a)
	{
		this -> name = name;
		this -> a = a;
	}
	
	bool operator==(const person &p)
	{
		if(this -> name == p.name && this -> a == p.a)
			return true;
		else return false;
	}
	string name;
	int a;
};

int main()
{
	vector v;
	
	person p1("aa",99);
	v.push_back(p1);
	
	vector::iterator it = find(v.begin(),v.end(),p1);
	
	if(it != v.end()) cout << "找到了" << endl;
}

 

find_if 

#include
using namespace std;

class dayu5
{
public:
	bool operator()(int v)
	{
		return v > 5;
	}
};

int main()
{
	vector v;
	v.push_back(3);
	v.push_back(2);
	v.push_back(9);
	v.push_back(4);
	v.push_back(10);
	
	vector::iterator it = find_if(v.begin(),v.end(),dayu5());
	if(it != v.end()) cout << "找到了" << endl;
}

adjacent_find

 

#include
using namespace std;

int main()
{
	vector v;
	v.push_back(3);
	v.push_back(2);
	v.push_back(3);
	v.push_back(4);
	v.push_back(4);
	
	vector::iterator it = adjacent_find(v.begin(),v.end());
	
	cout << *it << endl;
}

 

binary_search

 

必须是有序的序列 

#include
using namespace std;

int main()
{
	vector v;
	v.push_back(1);
	v.push_back(2);
	v.push_back(3);
	v.push_back(4);
	v.push_back(4);
	
	bool ret = binary_search(v.begin(),v.end(),3);
	cout << ret << endl;
	
	return 0;

}

 

count

 

统计自定义数据类型数目时，要重载==符号 

#include
using namespace std;

int main()
{
	vector v;
	v.push_back(1);
	v.push_back(2);
	v.push_back(3);
	v.push_back(4);
	v.push_back(4);
	
	int num = count(v.begin(),v.end(),4);
	cout << num << endl;
	
	return 0;
}

 

count_if

 

#include
using namespace std;

class dayu2
{
public:
	bool operator()(int v)
	{
		return v > 2;
	}
};

int main()
{
	vector v;
	v.push_back(1);
	v.push_back(2);
	v.push_back(3);
	v.push_back(4);
	v.push_back(4);
	
	int num = count_if(v.begin(),v.end(),dayu2());
	cout << num << endl;
	
	return 0;
}