STL学习(五)--set/multiset用法详解

头文件set
http://blog.csdn.net/longshengguoji/article/details/8546286
set和multiset是集合类非线性，差距是set中不允许有重复的元素，而multiset中允许有重复的元素。
set和multisets都以平衡二叉树实现
平衡二叉树:
它是一 棵空树或它的左右两个子树的高度差的绝对值不超过1，并且左右两个子树都是一棵平衡二叉树。

常用函数
1)构造函数和析构函数
set< > c;//其实看了前面的就差不多知道后面的和前面的在构造上应该没有多大的差别
set<> c(op);//以op为排序准则，产生一个空的set
multiset<> c1(op);//以op为排序准则，产生一个空的set
如果当前迭代器指向的元素被删除则迭代器失效

#include   
#include 

using namespace std;

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  

    for (auto Iter = third.begin(); Iter != third.end(); Iter++)
    {
        cout << *Iter << " ";
    }
    cout << endl;

    return 0;
}

2)大小，判断空函数
3)增加删除函数
pair

#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)
    {
        std::cout << "有重复的\n";
        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)
    {
        if (*it == 10)
        {
            myset.erase(it++);
            it--;
            continue;
        }
        std::cout << ' ' << *it;
    }
    std::cout << '\n';

    return 0;
}

关于erase的用法

#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;
}

4)遍历函数
5)操作函数
const_iterator lower_bound(const Key& key);//返回容器中大于等于key的迭代器指针
const_iterator upper_bound(const Key& key);//返回容器中大于key的迭代器指针
int count(const Key& key) const;//返回容器中元素等于key的元素的个数
pair

#include 
#include 

using namespace std;

int main()
{
    multiset<int> myset;

    for (int i = 1; i <= 5; i++)
    {
        if (i == 4)
        {
            myset.insert(i * 10);
        }
        myset.insert(i * 10);   // myset: 10 20 30 40 50  
    }

    pair<set<int>::const_iterator, set<int>::const_iterator> ret;
    ret = myset.equal_range(40);

    cout << "the lower bound points to: " << *ret.first << '\n';//返回区间的第一个
    cout << "the upper bound points to: " << *ret.second << '\n';//返回区间最后一个的下一个

    auto iter = ret.first;
    for (iter; iter != ret.second; iter++)
    {
        cout << *iter << " ";
    }
    cout << endl;
    return 0;
}

关于swap

#include   
#include 

using namespace std;

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

    first.swap(second);

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

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

    return 0;
}