3.成員查找

STL中支持多種查找方式。

• find() --查找指定元素
• find_if() --按條件查找
• adjacend_find() --查找相鄰元素
• binary_search() --二分法查找
• count() --統(tǒng)計元素個數(shù)
• count_if() --按條件統(tǒng)計

3.1 find查找

find函數(shù)：
find(_InIt _First, const _InIt _Last, const _Ty& _Val);
   _First、_Last  --查找的起始和結束位置
   _Val  --要查找的內容
返回值：成功返回查找到位置的迭代器
        失敗返回end();

#include 
using namespace std;
#include 
#include 
#include 
#include 
#include 
class Person
{
	friend class map_compare;
	friend class print;
	friend ostream& operator p.age;
	}
private:
	string name;
	int age;
};
ostream& operatorvtr;
	vtr.push_back(Person("小王", 18));
	vtr.push_back(Person("小劉", 17));
	vtr.push_back(Person("小李", 22));
	vtr.push_back(Person("小林", 19));
	for_each(vtr.begin(),vtr.end(),print());
	vector::iterator ret=find(vtr.begin(), vtr.end(), Person("小劉", 17));
	if (ret == vtr.end())
	{
		cout t;
	t.push_back(Person("小王", 18));
	t.push_front(Person("小劉", 17));
	t.insert(t.end(),Person("小王", 18));
	t.insert(t.begin(), Person("小王", 18));
	t.push_back(Person("小李", 22));
	t.push_back(Person("小林", 19));
	for_each(t.begin(), t.end(), print());
	cout ::iterator ptr = t.begin();ptr != t.end(); )
	{
		ptr =find(ptr, t.end(), Person("小王", 18));
		if (ptr != t.end())
		{
			cout s;
	s.push(Person("小王", 18));
	s.push(Person("小劉", 17));
	s.push(Person("小李", 22));
	s.push(Person("小林", 19));
	s.push(Person("小王", 18));
	cout & p)
	{
		cout & p1, const pair& p2)
	{
		if (p1.first == p2.first && p1.second == p2.second)return true;
		return false;
	}

};
//map容器
void multimap_test()
{
	cout mp;
	//插入數(shù)據(jù)
	mp.insert(pair(Person("小王", 18), 88));
	mp.insert(make_pair(Person("小劉", 17), 99));
	mp.insert(multimap::value_type(Person("小王", 18), 100));
	mp.insert(make_pair(Person("小李", 19), 95));
	for_each(mp.begin(), mp.end(), map_print());
	cout::iterator ret = mp.find(Person("小王", 18));//查找數(shù)據(jù)
	map_print p;
	//multimap容器由于數(shù)據(jù)都是有序的，所以相同的數(shù)據(jù)都是連在一起的
	for (int i = 0; i < mp.count(Person("小王", 18)); i++, ret++)
	{
		if (ret != mp.end())
		{
			p(*ret);
		}
	}
}
class stu
{
public:
	stu() {}
	stu(string name, int age) :name(name), age(age) {
	}
	bool operator==(const stu& p)const
	{
		if (name == p.name && age == p.age)return true;
		return false;
	}
	bool operator p.age;
	}
	string name;
	int age;
};
int main()
{
	vec_test();
	list_test();
	stack_test();
	multimap_test();
	system("pause");
}
#endif

3.2 find_if條件查找

find_if(_InIt _First, const _InIt _Last, _Pr _Pred)
形參：_First、_Last --查找的起始和結束迭代器
	 _Pred  --仿函數(shù)，查找條件
返回值：成功返回查找到的成員的位置迭代器
        失敗返回endl

#include 
#include 
#include 
#include 
#include 
using namespace std;
class Person
{
	friend std::ostream& operator(const Person& p)const
	{
		return age > p.age;
	}
private:
	std::string name;
	int age;
};
std::ostream& operator 18;
	}
	bool operator()(const Person& p1, const Person& p2)const
	{
		if (p1.age == p2.age)return p1.name < p2.name;
		return p1.age < p2.age;
	}

};
class print
{
public:
	void operator()(pairp)
	{
		cout  vtr;
	vtr.push_back(Person("小王", 18));
	vtr.push_back(Person("小劉", 17));
	vtr.push_back(Person("小李", 22));
	vtr.push_back(Person("小林", 19));
	std::cout ::iterator ret=find_if(vtr.begin(), vtr.end(), compare());
	if (ret != vtr.end())
	{
		std::cout p;
	p.insert(make_pair(Person("小王", 18), 88));
	p.insert(make_pair(Person("小劉", 17), 99));
	p.insert(make_pair(Person("小劉", 17), 77));
	p.insert(make_pair(Person("小林", 17), 77));
	p.insert(make_pair(Person("小李", 22), 100));
	for_each(p.begin(), p.end(), print());
	cout ::iterator,multimap::iterator> ret=p.equal_range(Person("小劉", 17));
	for (; ret.first != ret.second;ret.first++)
	{
		print temp;
		temp(*(ret.first));
	}
}
int main()
{
	vector_test();
	multimap_test();
	system("pause");
}

3.3 find_if條件查找

adjacent_find() -查找相鄰重復元素，查找成功返回相鄰重復元素的首位置的迭代器，失敗返回end
iterator adjacent_find(const _FwdIt _First, _FwdIt _Last, _Pr _Pred)
形參：_First、_Last --要查找的起始、結束區(qū)間迭代器
      _Pred --查找條件
返回值：成功返回相鄰重復元素的首位置的迭代器
        失敗返回end

示例：

#include 
#include 
#include 
#include 
using namespace std;
class Person
{
	friend ostream& operatorage && p.name == name)return true;
		return false;
	}
	string name;
	int age;
};
ostream& operatorvtr;
	vtr.push_back(Person("小王", 18));
	vtr.push_back(Person("小劉", 18));
	vtr.push_back(Person("小王", 18));
	vtr.push_back(Person("小王", 18));
	vtr.push_back(Person("小李", 18));
	auto ret=adjacent_find(vtr.begin(), vtr.end(), compare());
	if (ret != vtr.end())
	{
		cout  p)const
	{
		cout  17;
	}

};
void mulitmap_test()
{
	cout mp;
	mp.insert(make_pair(Person("小王", 16), 77));
	mp.insert(make_pair(Person("小劉", 18), 88));
	mp.insert(make_pair(Person("小劉", 18), 88));
	mp.insert(make_pair(Person("小李", 19), 99));
	cout 

3.4 二分法查找binary_search

二分法查找元素:
	bool binary_search(val); -->查找成功返回true,失敗返回false，保證數(shù)據(jù)順序為從小到大
	binary_search(_FwdIt _First, _FwdIt _Last, const _Ty& _Val, _Pr _Pred)
	形參：_First、_Last --起始和結束迭代器
	      _Val --要查找的內容
		  _Pred  --數(shù)據(jù)順序方式(默認從小到大)
注意：調用該函數(shù)必須保證有序，否結果可能不準確

#include 
#include 
#include 
#include 
using namespace std;
class Print
{
public:
	void operator()(int v1)
	{
		cout vtr;
	vtr.push_back(10);
	vtr.push_back(3);
	vtr.push_back(6);
	vtr.push_back(2);
	vtr.push_back(5);
	cout ());
	for_each(vtr.begin(), vtr.end(), Print());
	cout 

3.5 查找個數(shù)count

查找指定成員個數(shù):
	count(const _InIt _First, const _InIt _Last, const _Ty& _Val)-->返回查找到的個數(shù)
	形參：_First、_Last --起始和結束迭代器
	      _Val --要查找的內容
	返回值：返回查找到的個數(shù)

示例：

#include 
using namespace std;
#include 
#include 
class Person
{
public:
	Person() {}
	Person(string name, int age) :name(name), age(age) {

	}
	bool operator==(const Person p)const
	{
		if (age == p.age && name == p.name)return true;
		return false;
	}
	bool operator==(const int age)const
	{
		if (this->age == age)return true;
		return false;
	}
	string name;
	int age;
};
class compare
{
public:
	bool operator()(const Person p1, const Person p2)const
	{
		if (p1.age == p2.age && p1.name == p2.name)return true;
		return false;
	}
};
void test()
{
	vector vtr;
	vtr.push_back(Person("小王", 18));
	vtr.push_back(Person("小劉", 22));
	vtr.push_back(Person("小王", 18));
	vtr.push_back(Person("小林", 17));
	vtr.push_back(Person("小王", 18));
	vtr.push_back(Person("小蔣", 20));
	auto cnt=count(vtr.begin(), vtr.end(), Person("小王", 18));
	cout 

3.5 查找個數(shù)count

按條件查找:
	count_if(_InIt _First, _InIt _Last, _Pr _Pred);--返回查找到個數(shù)
	形參：_First、_Last --起始和結束迭代器
	      _Pred  --查找條件
	返回值：返回查找到的元素位置的迭代器
	        失敗返回end()

#include 
#include 
#include 
using namespace std;
class Person
{
public:
	Person() {}
	Person(string name, int age) :name(name), age(age) {

	}
	string name;
	int age;
};
class Compare
{
public:
	bool operator()(const Person& p)const
	{
		if (p.name == "小王" && p.age > 18)return true;
		return false;
	}

};
void test()
{
	vectorvtr;
	vtr.push_back(Person("小王", 18));
	vtr.push_back(Person("小劉", 22));
	vtr.push_back(Person("小王", 19));
	vtr.push_back(Person("小林", 17));
	vtr.push_back(Person("小王", 22));
	vtr.push_back(Person("小蔣", 20));
	auto ret=count_if(vtr.begin(), vtr.end(), Compare());
	cout