集合是使用STL中的C++语言实现的容器，其概念类似于数学中定义集合的方式。将集合与其他容器分开的事实是它仅包含不同的元素，并且可以按排序顺序遍历元素。在竞争性编程和解决算法问题中，拥有牢固的集合很有用。本文讨论了STL集中的插入和删除。
插入
- insert(ele) ：此函数将元素插入集合中。插入只会发生时传递的元素是不是已经在集。它返回一个指针对。指向已经存在或新插入的元素的第一个元素。返回布尔状态为“ true”或“ false”的第二个元素。
- insert(hint，ele) ：在此实现中，提示指针与要插入的元素一起发送。提示指针的使用是为了帮助insert()知道实际的插入位置。因此，尝试减少分配元素的时间。提示指针不会在特定位置强制插入。此函数将指针返回到插入元素的位置。
- insert(beg_ptr，end_ptr) ：这种插入类型是将其他容器的元素插入集合中所必需的。如果源容器中存在重复的元素，则不会将其插入。
使用insert() ：插入函数用于将元素插入集合中。插入后，将对元素进行重新排序，并对集合进行排序。此函数以3种方式实现。
// C++ code to demonstrate the working of insert()
#include
#include // for set operations
using namespace std;
int main()
{
// declaring set
set st;
// declaring iterators
set::iterator it = st.begin();
set::iterator it1, it2;
// declaring pair for return value of set containing
// set iterator and bool
pair< set::iterator,bool> ptr;
// using insert() to insert single element
// inserting 20
ptr = st.insert(20);
// checking if the element was already present or newly inserted
if (ptr.second)
cout << "The element was newly inserted" ;
else cout << "The element was already present" ;
// printing set elements after insertion
cout << "\nThe set elements after 1st insertion are : ";
for (it1 = st.begin(); it1!=st.end(); ++it1)
cout << *it1 << " ";
// inserting set elements using hint
st.insert(it, 24);
// printing set elements after insertion
cout << "\nThe set elements after 2nd insertion are : ";
for (it1 = st.begin(); it1!=st.end(); ++it1)
cout << *it1 << " ";
// inserting array elements in set
// 24 is not inserted again
int arr[3] = { 25, 24, 26 };
st.insert(arr, arr+3);
// printing set elements after insertion
cout << "\nThe set elements after 3rd insertion are : ";
for (it1 = st.begin(); it1!=st.end(); ++it1)
cout << *it1 << " ";
}
输出：
The element was newly inserted
The set elements after 1st insertion are : 20
The set elements after 2nd insertion are : 20 24
The set elements after 3rd insertion are : 20 24 25 26
- emplace() ：使用就地构造策略插入元素。将set的大小增加1。返回一个指针对。第一个元素是迭代器，它指向插入元素的位置。 2nd返回一个布尔变量，指示一个已经存在或新创建的元素。
- emplace_hint() ：使用“ hint_iterator”来获得插入位置的提示，以可能减少插入所插入元素所需的时间。这不会影响插入位置。它发生在内部定义的地方。
使用emplace ：emplace也用于将元素插入Set中。此函数类似于上面讨论的“ insert()”，唯一的区别是元素的“就地”构造发生在元素插入的位置，而不是复制或电影现有对象的insert()。
// C++ code to demonstrate the working of emplace()
// and emplace_hint()
#include
#include // for set operations
using namespace std;
int main()
{
// declaring set
set st;
// declaring iterators
set::iterator it = st.begin();
set::iterator it1, it2;
// declaring pair for return value of set containing
// set iterator and bool
pair< set::iterator,bool> ptr;
// using emplace() to insert single element
// inserting 24
ptr = st.emplace(24);
// checking if the element was already present or
// newly inserted returns true. newly inserted
if (ptr.second)
cout << "The element was newly inserted" ;
else cout << "The element was already present" ;
// printing set elements after insertion
cout << "\nThe set elements after 1st insertion are : ";
for (it1 = st.begin(); it1!=st.end(); ++it1)
cout << *it1 << " ";
// using emplace() to insert single element
// inserting 24 // not inserted this time
ptr = st.emplace(24);
// checking if the element was already present or
// newly inserted returns false. already inserted
if (ptr.second)
cout << "\nThe element was newly inserted" ;
else cout << "\nThe element was already present" ;
// printing set elements after insertion
cout << "\nThe set elements after 2nd insertion are : ";
for (it1 = st.begin(); it1!=st.end(); ++it1)
cout << *it1 << " ";
// inserting set elements using hint
st.emplace_hint(it,25);
// printing set elements after insertion
cout << "\nThe set elements after 3rd insertion are : ";
for (it1 = st.begin(); it1!=st.end(); ++it1)
cout << *it1 << " ";
}
输出：
The element was newly inserted
The set elements after 1st insertion are : 24
The element was already present
The set elements after 2nd insertion are : 24
The set elements after 3rd insertion are : 24 25
删除中
- delete(num) ：擦除其参数中提到的值。删除后对集重新排序。
- delete(iter) ：擦除其参数中提到的迭代器指向的位置的值。
- delete(strt_iter，end_iter) ：擦除从“ strt_iter”到“ end_iter”的元素范围。
使用擦除() ：擦除()用于擦除参数中提到的集合中的元素，包括其位置，其值或数字范围。
// C++ code to demonstrate the working of erase()
#include
#include // for set operations
using namespace std;
int main()
{
// declaring set
set st;
// declaring iterators
set::iterator it;
set::iterator it1;
set::iterator it2;
// declaring pair for return value of set containing
// set iterator and bool
pair< set::iterator,bool> ptr;
// inserting values in set
for (int i=1; i<10; i++)
st.insert(i*5);
// printing initial set elements
cout << "The set elements after insertion are : ";
for (it1 = st.begin(); it1!=st.end(); ++it1)
cout << *it1 << " ";
it = st.begin();
cout << endl;
// erasing element using iterator
// erases 2nd element i.e., 10
++it;
st.erase(it);
// printing set elements after deletion
cout << "The set elements after 1st deletion are : ";
for (it1 = st.begin(); it1!=st.end(); ++it1)
cout << *it1 << " ";
// erasing element using value
st.erase(40);
// printing set elements after deletion
cout << "\nThe set elements after 2nd deletion are : ";
for (it1 = st.begin(); it1!=st.end(); ++it1)
cout << *it1 << " ";
++it;
++it;
++it;
++it;
// erasing element using range iterator
// deletes 25 - last(45)
st.erase(it, st.end());
// printing set elements 3rd deletion
cout << "\nThe set elements after 3rd deletion are : ";
for (it1 = st.begin(); it1!=st.end(); ++it1)
cout << *it1 << " ";
cout << endl;
}
输出：
The set elements after insertion are : 5 10 15 20 25 30 35 40 45
The set elements after 1st deletion are : 5 15 20 25 30 35 40 45
The set elements after 2nd deletion are : 5 15 20 25 30 35 45
The set elements after 3rd deletion are : 5 15 20
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