上一篇：《STL源码剖析》笔记-RB-tree

set容器的特性就是所有元素都会根据键值进行自动排序，和map不同的是set的键值就是实值。并且通过set的迭代器无法改变set的键值，因为改变键值会打破set的排序。set排序的特性能够由rb-tree实现且所需接口rb-tree都已经提供，所以set底层采用了rb-tree。

// 默认使用递增排序
template <class Key, class Compare = less<Key>, class Alloc = alloc>
class set {
public:    typedef Key key_type;typedef Key value_type;typedef Compare key_compare;typedef Compare value_compare;
private:// 底层为rb-treetypedef rb_tree<key_type, value_type,identity<value_type>, key_compare, Alloc> rep_type;rep_type t; 
public:// 指针、迭代器、引用都是const类型，限制了不能修改键值typedef typename rep_type::const_pointer pointer;typedef typename rep_type::const_pointer const_pointer;typedef typename rep_type::const_reference reference;typedef typename rep_type::const_reference const_reference;typedef typename rep_type::const_iterator iterator;typedef typename rep_type::const_iterator const_iterator;typedef typename rep_type::const_reverse_iterator reverse_iterator;typedef typename rep_type::const_reverse_iterator const_reverse_iterator;typedef typename rep_type::size_type size_type;typedef typename rep_type::difference_type difference_type;// 构造函数set() : t(Compare()) {}explicit set(const Compare& comp) : t(comp) {}// 区间赋值构造，使用insert_unique函数保证插入键值唯一template <class InputIterator>set(InputIterator first, InputIterator last): t(Compare()) { t.insert_unique(first, last); }template <class InputIterator>set(InputIterator first, InputIterator last, const Compare& comp): t(comp) { t.insert_unique(first, last); }// 拷贝/赋值构造set(const set<Key, Compare, Alloc>& x) : t(x.t) {}set<Key, Compare, Alloc>& operator=(const set<Key, Compare, Alloc>& x) {t = x.t;return *this;}// set操作，使用rb-tree接口key_compare key_comp() const { return t.key_comp(); }value_compare value_comp() const { return t.key_comp(); }iterator begin() const { return t.begin(); }iterator end() const { return t.end(); }reverse_iterator rbegin() const { return t.rbegin(); }reverse_iterator rend() const { return t.rend(); }bool empty() const { return t.empty(); }size_type size() const { return t.size(); }size_type max_size() const { return t.max_size(); }void swap(set<Key, Compare, Alloc>& x) { t.swap(x.t); }// 插入、删除typedef  pair<iterator, bool> pair_iterator_bool;pair<iterator,bool> insert(const value_type& x) {pair<typename rep_type::iterator, bool> p = t.insert_unique(x);return pair<iterator, bool>(p.first, p.second);}iterator insert(iterator position, const value_type& x) {typedef typename rep_type::iterator rep_iterator;return t.insert_unique((rep_iterator&)position, x);}template <class InputIterator>void insert(InputIterator first, InputIterator last) {t.insert_unique(first, last);}void erase(iterator position) {typedef typename rep_type::iterator rep_iterator;t.erase((rep_iterator&)position);}size_type erase(const key_type& x) {return t.erase(x);}void erase(iterator first, iterator last) {typedef typename rep_type::iterator rep_iterator;t.erase((rep_iterator&)first, (rep_iterator&)last);}void clear() { t.clear(); }iterator find(const key_type& x) const { return t.find(x); }size_type count(const key_type& x) const { return t.count(x); }iterator lower_bound(const key_type& x) const {return t.lower_bound(x);}iterator upper_bound(const key_type& x) const {return t.upper_bound(x);}pair<iterator,iterator> equal_range(const key_type& x) const {return t.equal_range(x);}friend bool operator== __STL_NULL_TMPL_ARGS (const set&, const set&);friend bool operator< __STL_NULL_TMPL_ARGS (const set&, const set&);
};template <class Key, class Compare, class Alloc>
inline bool operator==(const set<Key, Compare, Alloc>& x,const set<Key, Compare, Alloc>& y) {return x.t == y.t;
}template <class Key, class Compare, class Alloc>
inline bool operator<(const set<Key, Compare, Alloc>& x,const set<Key, Compare, Alloc>& y) {return x.t < y.t;
}

set使用

#include <set>int main(int argc, char* argv[])
{std::set<int> st = {0, 1, 3, 5};for (auto i : st){std::cout << i;}std::cout << std::endl;st.insert(4);for (auto i : st){std::cout << i;}std::cout << std::endl;st.insert(1);       // 已经存在插入无效for (auto i : st){std::cout << i;}std::cout << std::endl;auto result = st.find(1);if (result  != st.end()){st.erase(result);}for (auto i : st){std::cout << i;}std::cout << std::endl;return 0;
}// 输出结果：
0135
01345
01345
0345

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