（七）set类的主要成员
set<T>是一种集合容器。
☆void clear();//删除所有元素
☆size_type count(const key_type& x)const; //返回键为x的元素的个数
☆bool empty() const; //返回是否为空
☆void erase(iterator position);//删除在位置position的元素
☆size_type erase(const key_type& x);//删除索引为x的元素 如果是multiset则索引为x的全部都删除
☆void erase(iterator first, iterator last);//删除在[first，last]间的元素
☆iterator find(const key_type& x)const;//返回索引为x的元素的指针
☆pair<iterator,bool>insert(const value_type& x);//返回<指向元素x的迭代器，是否插入成功>
☆interator lower_bound(const key_type& x)const; //返指向键不小于x的第一个元素的迭代器
☆size_type size() const;//返回set的大小
☆void swap(set& X);//与setX交换内容
☆iterator upper_bound(const key_type& x)const;//返回指向键大于x的第一个元素的迭代器
STL-set用法
// 1.set::begin/end
#include <iostream>
#include <set>
using namespace std;
int main ()
{
int myints[] = {75,23,65,42,13,13};
set<int> myset (myints,myints+6);
set<int>::iterator it;
cout << "myset contains:";
for ( it=myset.begin() ; it != myset.end(); it++ )
cout << " " << *it;
cout << endl;
return 0;
}
Output:
myset contains: 13 23 42 65 75
// 2.set::empty
#include <iostream>
#include <set>
using namespace std;
int main ()
{
set<int> myset;
myset.insert(20);
myset.insert(30);
myset.insert(10);
cout << "myset contains:";
while (!myset.empty())
{
cout << " " << *myset.begin();
myset.erase(myset.begin());
}
cout << endl;
return 0;
}
Output:myset contains: 10 20 30
// 3.set::size
#include <iostream>
#include <set>
using namespace std;
int main ()
{
set<int> myints;
cout << "0. size: " << (int) myints.size() << endl;
for (int i=0; i<10; i++) myints.insert(i);
cout << "1. size: " << (int) myints.size() << endl;
myints.insert (100);
cout << "2. size: " << (int) myints.size() << endl;
myints.erase(5);
cout << "3. size: " << (int) myints.size() << endl;
return 0;
}
Output:0. size: 0
1. size: 10
2. size: 11
3. size: 10
// 4.set::find
#include <iostream>
#include <set>
using namespace std;
int main ()
{
set<int> myset;
set<int>::iterator it;
// set some initial values:
for (int i=1; i<=5; i++) myset.insert(i*10); // set: 10 20 30 40 50
it=myset.find(20);
myset.erase (it);
myset.erase (myset.find(40));
cout << "myset contains:";
for (it=myset.begin(); it!=myset.end(); it++)
cout << " " << *it;
cout << endl;
return 0;
}
Output:
myset contains: 10 30 50
// 5.set::count
#include <iostream>
#include <set>
using namespace std;
int main ()
{
set<int> myset;
int i;
// set some initial values:
for (i=1; i<5; i++) myset.insert(i*3); // set: 3 6 9 12
for (i=0;i<10; i++)
{
cout << i;
if (myset.count(i)>0)
cout << " is an element of myset.\n";
else
cout << " is not an element of myset.\n";
}
return 0;
}
Output:
0 is not an element of myset.
1 is not an element of myset.
2 is not an element of myset.
3 is an element of myset.
4 is not an element of myset.
5 is not an element of myset.
6 is an element of myset.
7 is not an element of myset.
8 is not an element of myset.
9 is an element of myset.
// 6.set::lower_bound/upper_bound
#include <iostream>
#include <set>
using namespace std;
int main ()
{
set<int> myset;
set<int>::iterator it,itlow,itup;
for (int i=1; i<10; i++) myset.insert(i*10); // 10 20 30 40 50 60 70 80 90
itlow=myset.lower_bound (30); // ^
itup=myset.upper_bound (60); // ^
myset.erase(itlow,itup); // 10 20 70 80 90
cout << "myset contains:";
for (it=myset.begin(); it!=myset.end(); it++)
cout << " " << *it;
cout << endl;
return 0;
}
Notice that lower_bound(30) returns an iterator to 30, whereas upper_bound(60) returns an iterator to 70.
myset contains: 10 20 70 80 90
// 7.set::equal_elements
#include <iostream>
#include <set>
using namespace std;
int main ()
{
set<int> myset;
pair<set<int>::iterator,set<int>::iterator> ret;
for (int i=1; i<=5; i++) myset.insert(i*10); // set: 10 20 30 40 50
ret = myset.equal_range(30);
cout << "lower bound points to: " << *ret.first << endl;
cout << "upper bound points to: " << *ret.second << endl;
return 0;
}
lower bound points to: 30
upper bound points to: 40