c++ set

参考链接：http://www.cplusplus.com/reference/set/set/find/

顺序容器	顺序容器适配器	关联容器
vector（支持快速随机访问）	stack（LIFO栈）	set（红黑树，高效的平衡检索二叉树）
list（支持快速插入/删除）	queue（FIFO队列）	map
deque（双端队列）	priority_queue（有优先级管理的队列）

顺序容器提供了快速顺序访问元素的能力。
关联容器支持高效的关键字查找和访问。

一、set容器分类

1. set：关键字即值，只保存唯一的关键字
2. multiset：关键字可重复出现

二、set具备的两个特点

1. set中的元素都是拍好序的
2. ser中的元素都是唯一的（有的比赛解题用这个思路还是很方便的）

三、set用法

1. set::begin

// set::begin/end
#include 
#include 

int main ()
{
  int myints[] = {75,23,65,42,13};
  std::set<int> myset (myints,myints+5);

  std::cout << "myset contains:";
  for (std::set<int>::iterator it=myset.begin(); it!=myset.end(); ++it)
    std::cout << ' ' << *it;

  std::cout << '\n';

  return 0;
}
//Output:
//myset contains: 13 23 42 65 75

2. set::end

// set::begin/end
#include 
#include 

int main ()
{
  int myints[] = {75,23,65,42,13};
  std::set<int> myset (myints,myints+5);

  std::cout << "myset contains:";
  for (std::set<int>::iterator it=myset.begin(); it!=myset.end(); ++it)
    std::cout << ' ' << *it;

  std::cout << '\n';

  return 0;
}
//Output:
//myset contains: 13 23 42 65 75

3. insert（有序，唯一）

• 简单：

#include
#include
using namespace std;
int main(){
	set<int> mySet;
	mySet.insert(5);
	mySet.insert(3);
	mySet.insert(4);
	mySet.insert(4);
	
	cout << "mySet contains:";
	for(set<int>::iterator it=mySet.begin(); it!=mySet.end(); ++it){
		cout<< ' ' << *it;
	}
	
	cout << '\n';
	
	return 0;
} 
//Output：
//mySet contains: 3 4 5

• 较复杂

#include 
#include 

int main ()
{
  std::set<int> myset;
  std::set<int>::iterator it;
  std::pair<std::set<int>::iterator,bool> ret;

  // set some initial values:
  for (int i=1; i<=5; ++i) myset.insert(i*10);    // set: 10 20 30 40 50

  ret = myset.insert(20);               // no new element inserted

  if (ret.second==false) it=ret.first;  // "it" now points to element 20

  myset.insert (it,25);                 // max efficiency inserting
  myset.insert (it,24);                 // max efficiency inserting
  myset.insert (it,26);                 // no max efficiency inserting

  int myints[]= {5,10,15};              // 10 already in set, not inserted
  myset.insert (myints,myints+3);

  std::cout << "myset contains:";
  for (it=myset.begin(); it!=myset.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}
//Output:
//myset contains: 5 10 15 20 24 25 26 30 40 50

4. set::clear

#include 
#include 

int main ()
{
  std::set<int> myset;

  myset.insert (100);
  myset.insert (200);
  myset.insert (300);

  std::cout << "myset contains:";
  for (std::set<int>::iterator it=myset.begin(); it!=myset.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  myset.clear();
  myset.insert (1101);
  myset.insert (2202);

  std::cout << "myset contains:";
  for (std::set<int>::iterator it=myset.begin(); it!=myset.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}
//Output//
//myset contains: 100 200 300
//myset contains: 1101 2202

5. erase

#include 
#include 

int main ()
{
  std::set<int> myset;
  std::set<int>::iterator it;

  // insert some values:
  for (int i=1; i<10; i++) myset.insert(i*10);  // 10 20 30 40 50 60 70 80 90

  it = myset.begin();
  ++it;                                         // "it" points now to 20

  myset.erase (it);

  myset.erase (40);

  it = myset.find (60);
  myset.erase (it, myset.end());

  std::cout << "myset contains:";
  for (it=myset.begin(); it!=myset.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
 }
//Output
//myset contains: 10 30 50

6. set::find

#include 
#include 

int main ()
{
  std::set<int> myset;
  std::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));

  std::cout << "myset contains:";
  for (it=myset.begin(); it!=myset.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}
//Output：
//myset contains: 10 30 50

7. set::size

#include 
#include 

int main ()
{
  std::set<int> myints;
  std::cout << "0. size: " << myints.size() << '\n';

  for (int i=0; i<10; ++i) myints.insert(i);
  std::cout << "1. size: " << myints.size() << '\n';

  myints.insert (100);
  std::cout << "2. size: " << myints.size() << '\n';

  myints.erase(5);
  std::cout << "3. size: " << myints.size() << '\n';

  return 0;
}
//Output：
/*
0. size: 0
1. size: 10
2. size: 11
3. size: 10
*/

8. swap

#include 
#include 

main ()
{
  int myints[]={12,75,10,32,20,25};
  std::set<int> first (myints,myints+3);     // 10,12,75
  std::set<int> second (myints+3,myints+6);  // 20,25,32

  first.swap(second);

  std::cout << "first contains:";
  for (std::set<int>::iterator it=first.begin(); it!=first.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  std::cout << "second contains:";
  for (std::set<int>::iterator it=second.begin(); it!=second.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}
//Output：
/*
first contains: 20 25 32
second contains: 10 12 75
*/