STL关联式容器-map
目录
- 会根据元素键值自动被排序,所有元素都是 pair,同时拥有实值 value 和键值 key,其 pair 是 <key,pair>。键值不可改变,正值可以。
- 新增删除操作后,之前的迭代器依然有效。
- 以 RB-tree 为底层机制,和 set 一样也是调用即可。
1. 数据结构
#ifndef __SGI_STL_INTERNAL_MAP_H
#define __SGI_STL_INTERNAL_MAP_H
__STL_BEGIN_NAMESPACE
#if defined(__sgi) && !defined(__GNUC__) && (_MIPS_SIM != _MIPS_SIM_ABI32)
#pragma set woff 1174
#endif
#ifndef __STL_LIMITED_DEFAULT_TEMPLATES
template <class Key, class T, class Compare = less<Key>, class Alloc = alloc>
#else
template <class Key, class T, class Compare, class Alloc = alloc>
#endif
class map {
public:
// typedefs:
typedef Key key_type;
typedef T data_type;
typedef T mapped_type;
typedef pair<const Key, T> value_type;
typedef Compare key_compare;
class value_compare
: public binary_function<value_type, value_type, bool> {
friend class map<Key, T, Compare, Alloc>;
protected :
Compare comp;
value_compare(Compare c) : comp(c) {}
public:
bool operator()(const value_type& x, const value_type& y) const {
return comp(x.first, y.first);
}
};
private:
typedef rb_tree<key_type, value_type,
select1st<value_type>, key_compare, Alloc> rep_type;
rep_type t; // red-black tree representing map
public:
typedef typename rep_type::pointer pointer;
typedef typename rep_type::const_pointer const_pointer;
typedef typename rep_type::reference reference;
typedef typename rep_type::const_reference const_reference;
typedef typename rep_type::iterator iterator;
typedef typename rep_type::const_iterator const_iterator;
typedef typename rep_type::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;
// allocation/deallocation
map() : t(Compare()) {}
explicit map(const Compare& comp) : t(comp) {}
#ifdef __STL_MEMBER_TEMPLATES
template <class InputIterator>
map(InputIterator first, InputIterator last)
: t(Compare()) { t.insert_unique(first, last); }
template <class InputIterator>
map(InputIterator first, InputIterator last, const Compare& comp)
: t(comp) { t.insert_unique(first, last); }
#else
map(const value_type* first, const value_type* last)
: t(Compare()) { t.insert_unique(first, last); }
map(const value_type* first, const value_type* last, const Compare& comp)
: t(comp) { t.insert_unique(first, last); }
map(const_iterator first, const_iterator last)
: t(Compare()) { t.insert_unique(first, last); }
map(const_iterator first, const_iterator last, const Compare& comp)
: t(comp) { t.insert_unique(first, last); }
#endif /* __STL_MEMBER_TEMPLATES */
map(const map<Key, T, Compare, Alloc>& x) : t(x.t) {}
map<Key, T, Compare, Alloc>& operator=(const map<Key, T, Compare, Alloc>& x)
{
t = x.t;
return *this;
}
// accessors:
key_compare key_comp() const { return t.key_comp(); }
value_compare value_comp() const { return value_compare(t.key_comp()); }
iterator begin() { return t.begin(); }
const_iterator begin() const { return t.begin(); }
iterator end() { return t.end(); }
const_iterator end() const { return t.end(); }
reverse_iterator rbegin() { return t.rbegin(); }
const_reverse_iterator rbegin() const { return t.rbegin(); }
reverse_iterator rend() { return t.rend(); }
const_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(); }
T& operator[](const key_type& k) {
return (*((insert(value_type(k, T()))).first)).second;
}
void swap(map<Key, T, Compare, Alloc>& x) { t.swap(x.t); }
// insert/erase
pair<iterator,bool> insert(const value_type& x) { return t.insert_unique(x); }
iterator insert(iterator position, const value_type& x) {
return t.insert_unique(position, x);
}
#ifdef __STL_MEMBER_TEMPLATES
template <class InputIterator>
void insert(InputIterator first, InputIterator last) {
t.insert_unique(first, last);
}
#else
void insert(const value_type* first, const value_type* last) {
t.insert_unique(first, last);
}
void insert(const_iterator first, const_iterator last) {
t.insert_unique(first, last);
}
#endif /* __STL_MEMBER_TEMPLATES */
void erase(iterator position) { t.erase(position); }
size_type erase(const key_type& x) { return t.erase(x); }
void erase(iterator first, iterator last) { t.erase(first, last); }
void clear() { t.clear(); }
// map operations:
iterator find(const key_type& x) { return t.find(x); }
const_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) {return t.lower_bound(x); }
const_iterator lower_bound(const key_type& x) const {
return t.lower_bound(x);
}
iterator upper_bound(const key_type& x) {return t.upper_bound(x); }
const_iterator upper_bound(const key_type& x) const {
return t.upper_bound(x);
}
pair<iterator,iterator> equal_range(const key_type& x) {
return t.equal_range(x);
}
pair<const_iterator,const_iterator> equal_range(const key_type& x) const {
return t.equal_range(x);
}
friend bool operator== __STL_NULL_TMPL_ARGS (const map&, const map&);
friend bool operator< __STL_NULL_TMPL_ARGS (const map&, const map&);
};
template <class Key, class T, class Compare, class Alloc>
inline bool operator==(const map<Key, T, Compare, Alloc>& x,
const map<Key, T, Compare, Alloc>& y) {
return x.t == y.t;
}
template <class Key, class T, class Compare, class Alloc>
inline bool operator<(const map<Key, T, Compare, Alloc>& x,
const map<Key, T, Compare, Alloc>& y) {
return x.t < y.t;
}
#ifdef __STL_FUNCTION_TMPL_PARTIAL_ORDER
template <class Key, class T, class Compare, class Alloc>
inline void swap(map<Key, T, Compare, Alloc>& x,
map<Key, T, Compare, Alloc>& y) {
x.swap(y);
}
#endif /* __STL_FUNCTION_TMPL_PARTIAL_ORDER */
#if defined(__sgi) && !defined(__GNUC__) && (_MIPS_SIM != _MIPS_SIM_ABI32)
#pragma reset woff 1174
#endif
__STL_END_NAMESPACE
#endif /* __SGI_STL_INTERNAL_MAP_H */
2. 使用demo
.1. pair
pair<string, int>p1; 和 make_pair<string, ing>(); 使用方法
#include <iostream>
#include <string>
#include <vector>
using namespace std;
//将pair放入容器&initpair
int main(int argc, const char *argv[])
{
vector<pair<string, int> > vec;//初始化vector
pair<string, int> p1;//num.1
p1.first = "hello";
p1.second = 12 ;
vec.push_back(p1);
pair<string, int> p2("world", 22);//num.2
vec.push_back(p2);
vec.push_back(make_pair<string, int>("foo", 44));//num.3
for(vector<pair<string,int> >::iterator it = vec.begin(); //g++ main.cc -std=c++0x
it != vec.end();++it)
{
cout << "key: " << it->first << " val:"<< it->second << endl;
}
return 0;
}
.2. map
- count:仅仅能得出该元素是否存在。
- find: 能够返回该元素的迭代器 。
#include <iostream>
#include <string>
#include <vector>
#include <map>
#include <algorithm>
using namespace std;
//Red_black Tree
int main(int argc, const char *argv[])
{
map<string, int> m;
m["beijing"] = 2000;
m["hangzhou"] = 880;
m["shanghai"] = 1500;
// key --> value 采用二叉排序树对key排序
//两种打印方式
for(map<string, int>::const_iterator it = m.begin();
it != m.end();it++)
{
cout << it->first <<":" << it->second << endl;
}
for(const pair<int, string> &p: m) // -std=c++0x(C++11) 注意要用pair
cout << p.first << ":" << p.second << endl;
return 0;
}
3. multimap
- 与 map 基本相同,除 insert_unique 和 insert_equal 的使用不同外基本一致