set

Sets/Multisets：内部的元素依据其值自动排序，Set内的相同数值的元素只能出现一次，Multisets内可包含多个数值相同的元素，内部由二叉树实现（实际上基于红黑树(RB-tree）实现），便于查找；
map和multisets也一样

1.构造

// constructing sets
#include <iostream>
#include <set>

bool fncomp (int lhs, int rhs) {return lhs<rhs;}

struct classcomp {
  bool operator() (const int& lhs, const int& rhs) const
  {return lhs<rhs;}
};

int main ()
{
  std::set<int> first;                           // empty set of ints

  int myints[]= {10,20,30,40,50};
  std::set<int> second (myints,myints+5);        // range

  std::set<int> third (second);                  // a copy of second

  std::set<int> fourth (second.begin(), second.end());  // iterator ctor.

  std::set<int,classcomp> fifth;                 // class as Compare

  bool(*fn_pt)(int,int) = fncomp;
  std::set<int,bool(*)(int,int)> sixth (fn_pt);  // function pointer as Compare
//can first=second
  return 0;
}

2.操作

2.1容量大小

//size
//empty
//max_size

2.2modify access

/*
 * set element is order,and is only
 * modify access
 * insert erase swap clear
*/
#include <iostream>
#include <set>
#include<QDebug>
int main ()
{
  std::set<int> myset;

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

  int myints[]= {5,10,15};              // 10 already in set, not inserted
  myset.insert (myints,myints+3);       //myset contains: 5 10 15 20 30 40 50
  myset.insert(11);                     //myset contains: 5 10 11 15 20 30 40 50

  myset.erase(myset.cbegin());          //erase 5
  //myset.erase(myset.begin(),myset.begin()+3);链式存储,不能这样计算地址,可以如下:
  auto it=myset.find(15);
  myset.erase(myset.begin(),it);
  myset.erase(20);
  myset.clear();

  //first.swap(second)
  return 0;
}

2.3其他

//find count  lower_bound  upper_bound  equal_bound

// set::find
#include <iostream>
#include <set>

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;
}

// set::count
#include <iostream>
#include <set>

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

  // set some initial values:
  for (int i=1; i<5; ++i) myset.insert(i*3);    // set: 3 6 9 12

  for (int i=0; i<10; ++i)
  {
    std::cout << i;
    if (myset.count(i)!=0)
      std::cout << " is an element of myset.\n";
    else
      std::cout << " is not an element of myset.\n";
  }

  return 0;
}

// set::lower_bound/upper_bound
#include <iostream>
#include <set>

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

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

  return 0;
}