begin
iterator begin();
begin()函数返回一个迭代器指向map的第一个元素。
clear
void clear();
clear()函数删除map中的所有元素。
count
size_type count( const KEY_TYPE &key );
count()函数返回map中键值等于key的元素的个数。
begin
iterator begin();
返回指向当前集合中第一个元素的迭代器。
clear
void clear();
清除当前集合中的所有元素。
count
size_type count( const key_type &key );
返回当前集合中出现的某个值的元素的数目。
阅读全文
1、rbegin、rend——容器逆序输出的头和尾
#include <iostream>
#include <set>
#include <iomanip>
#include <string>
using namespace std;
template <class T>
class Member
{
public:
Member(T l, T f) : last(l), first(f) {}
void print() const // const !!!
{
cout.setf(ios::left);
cout << setw(15) << first.c_str()
<< last << endl;
}
private:
T first, last;
// const !!!
friend bool operator < (const Member& m1, const Member& m2)
{
return (m1.last < m2.last) ? true : false;
}
friend bool operator == (const Member& m1, const Member& m2)
{
return (m1.last == m2.last) ? true : false;
}
};
//===============================================
int main ()
{
typedef Member<string> M;
typedef set<M, less<M> > S;
M m("Frost","Robert");
S s;
s.insert(m);
s.insert(M("Smith","John"));
s.insert(M("Amstrong","Bill"));
s.insert(M("Bain","Linda"));
S::iterator It = s.begin();
while ( It != s.end() )
(It++)->print();
cout << endl;
S::reverse_iterator rI = s.rbegin();
while ( rI != s.rend() )
(rI++)->print();
return 0;
}
运行结果:
// Bill Amstrong
// Linda Bain
// Robert Frost
// John Smith
//
// John Smith
// Robert Frost
// Linda Bain
// Bill Amstrong
1、erase——从容器中删除某个元素或者某个区间
#include <iostream>
#include <set>
using namespace std;
void print (set<int, less<int> >& s)
{
set<int, less<int> >::iterator It;
for ( It = s.begin(); It != s.end(); It++ )
cout << *It << " ";
cout << endl;
}
//--------------------------------------------
int main ()
{
int ary[] = {1,2,3,2,3,4,8,2,5,6};
set<int, less<int> > s;
s.insert(ary,ary+10);
print(s);
// erase '2'
s.erase(2);
print(s);
set<int, less<int> >::iterator It;
It = s.find(5);
// erase '5'
s.erase(It);
print(s);
It = s.find(4);
// erase from It to the end of set
s.erase(It,s.end());
print(s);
return 0;
}
运行结果:
// 1 2 3 4 5 6 8
// 1 3 4 5 6 8
// 1 3 4 6 8
// 1 3
1、构造函数
#include <iostream>
#include <set>
int main ()
{
int ary[] = { 5,3,7,5,2,3,7,5,5,4 };
set<int> s1;
set<int, greater<int> > s2;
for ( int i=0; i<sizeof(ary)/sizeof(int); i++ )
{
s1.insert(ary[i]);
s2.insert(ary[i]);
}
set<int>::iterator It = s1.begin();
cout << "s1 : ";
while ( It != s1.end() )
cout << *(It++) << " ";
cout << endl;
It = s2.begin();
cout << "s2 : ";
while ( It != s2.end() )
cout << *(It++) << " ";
cout << endl;
// 第二种形式的构造
set<int> s3(ary,ary+3);
It = s3.begin();
cout << "s3 : ";
while ( It != s3.end() )
cout << *(It++) << " ";
cout << endl;
//拷贝构造
set<int, less > s4(s1);
It = s4.begin();
cout << "s4 : ";
while ( It != s4.end() )
cout << *(It++) << " ";
cout << endl;
return 0;
}
运行结果:
// s1 : 2 3 4 5 7
// s2 : 7 5 4 3 2
// s3 : 3 5 7
// s4 : 2 3 4 5 7
1、resize——减小或者扩大容器的容量
#include <iostream>
#include <list>
int main ()
{
list<int> l(10);
cout << "Size of list l = "
<< l.size();
l.resize(100);
cout << "After l.resize(100)" << endl;
cout << "Size of list l = "
<< l.size();
l.resize(5);
cout << "After l.resize(5)" << endl;
cout << "Size of list l = "
<< l.size();
return 0;
}
运行结果:
// Size of list l = 10After l.resize(100)
// Size of list l = 100After l.resize(5)
// Size of list l = 5
1、max_size——容器能申请到的最大容量
#include <iostream>
#include <list>
int main ()
{
list li(10);
cout << "size() of li = "
<< li.size() << endl;
cout << "max_size = "
<< li.max_size() << endl;
return 0;
}
运行结果:
// size() of li = 10
// max_size = 4294967295
1、assign——初始化或者重置容器内元素
#include <iostream>
#include <list>
#include <algorithm>
#include <iterator>
using namespace std;
int main ()
{
int ary[]={1,2,3,4,5};
list<int> l;
// 将数组ary分配给l容器
l.assign(ary,ary+5);
copy(l.begin(),l.end(),
ostream_iterator<int>(cout," "));
cout << endl;
// 用3个100替换l容器内容
l.assign(3,100);
copy(l.begin(),l.end(),
ostream_iterator<int>(cout," "));
cout << endl;
return 0;
}
运行结果:
// 1 2 3 4 5
// 100 100 100
1、push_back——将某个元素从容器后端入栈
#include <iostream>
#include <deque>
#include <string>
#include <iterator>
using namespace std;
template <class T>
class Name
{
public:
Name(T t) : name(t) {}
void print()
{
cout << name << " ";
}
private:
T name;
};
//=============================
int main ()
{
typedef Name<string> N;
typedef deque<N> D;
D d;
N n1("Robert");
N n2("Alex");
d.push_back(n1);
d.push_back(n2);
// unnamed object of the type Name
d.push_back(N("Linda"));
D::iterator It = d.begin();
while ( It != d.end() )
(It++)->print();
cout << endl;
return 0;
}
运行结果:
// Robert Alex Linda
1、end——容器迭代器最后一个元素的下一个迭代
#include <iostream>
#include <deque>
#include <iterator>
#include <numeric>
using namespace std;
int main ()
{
deque<int> d(5);
iota(d.begin(),d.end(),1);
deque<int>::iterator It = d.begin();
while ( It != d.end() )
cout << *It++ << " ";
cout << endl;
// deque容器的最后一个元素
It = d.end()-1;
cout << *It << endl;
return 0;
}
运行结果:
// 1 2 3 4 5
// 5
