C++ Map

map的基本操作函数：

begin()          返回指向map头部的迭代器
clear(）         删除所有元素
count()          返回指定元素出现的次数
empty()          如果map为空则返回true
end()            返回指向map末尾的迭代器
equal_range()    返回特殊条目的迭代器对
erase()          删除一个元素
find()           查找一个元素
get_allocator()  返回map的配置器
insert()         插入元素
key_comp()       返回比较元素key的函数
lower_bound()    返回键值>=给定元素的第一个位置
max_size()       返回可以容纳的最大元素个数
rbegin()         返回一个指向map尾部的逆向迭代器
rend()           返回一个指向map头部的逆向迭代器
size()           返回map中元素的个数
swap()            交换两个map
upper_bound()     返回键值>给定元素的第一个位置
value_comp()      返回比较元素value的函数

map最基本的构造函数

map<string , int >mapstring;         map<int ,string >mapint;
map<sring, char>mapstring;         map< char ,string>mapchar;
map<char ,int>mapchar;            map<int ,char >mapint；

map添加数据

map<int ,string> maplive;
maplive.insert(pair<int,string>(102,"aclive"));
maplive.insert(map<int,string>::value_type(321,"hai"));
maplive[112]="April"; //map中最简单最常用的插入添加！

map中元素的查找

find()函数返回一个迭代器指向键值为key的元素，如果没找到就返回指向map尾部的迭代器。
map<int ,string >::iterator l_it;
l_it=maplive.find(112);
if(l_it==maplive.end())
cout<<"we do not find 112"<<endl;
else cout<<"wo find 112"<<endl;

map中元素的删除

如果删除112；
map<int ,string >::iterator l_it;;
l_it=maplive.find(112);
if(l_it==maplive.end())
cout<<"we do not find 112"<<endl;
else  maplive.erase(l_it);  //delete 112;

map中 swap的用法

For example：
#include <map>
#include <iostream>
using namespace std;
int main( )
{
map <int, int> m1, m2, m3;
map <int, int>::iterator m1_Iter;

m1.insert ( pair <int, int>  ( 1, 10 ) );
m1.insert ( pair <int, int>  ( 2, 20 ) );
m1.insert ( pair <int, int>  ( 3, 30 ) );
m2.insert ( pair <int, int>  ( 10, 100 ) );
m2.insert ( pair <int, int>  ( 20, 200 ) );
m3.insert ( pair <int, int>  ( 30, 300 ) );

cout << "The original map m1 is:";
for ( m1_Iter = m1.begin( ); m1_Iter != m1.end( ); m1_Iter++ )
cout << " " << m1_Iter->second;
cout   << "." << endl;

// This is the member function version of swap
//m2 is said to be the argument map; m1 the target map
m1.swap( m2 );

cout << "After swapping with m2, map m1 is:";
for ( m1_Iter = m1.begin( ); m1_Iter != m1.end( ); m1_Iter++ )
cout << " " << m1_Iter -> second;
cout  << "." << endl;
cout << "After swapping with m2, map m2 is:";
for ( m1_Iter = m2.begin( ); m1_Iter != m2.end( ); m1_Iter++ )
cout << " " << m1_Iter -> second;
cout  << "." << endl;
// This is the specialized template version of swap
swap( m1, m3 );

cout << "After swapping with m3, map m1 is:";
for ( m1_Iter = m1.begin( ); m1_Iter != m1.end( ); m1_Iter++ )
cout << " " << m1_Iter -> second;
cout   << "." << endl;
}

map的sort问题：

For example：
#include <map>
#include <iostream>
using namespace std;
int main( )
{
map <int, int> m1;
map <int, int>::iterator m1_Iter;
m1.insert ( pair <int, int>  ( 1, 20 ) );
m1.insert ( pair <int, int>  ( 4, 40 ) );
m1.insert ( pair <int, int>  ( 3, 60 ) );
m1.insert ( pair <int, int>  ( 2, 50 ) );
m1.insert ( pair <int, int>  ( 6, 40 ) );
m1.insert ( pair <int, int>  ( 7, 30 ) );
cout << "The original map m1 is:"<<endl;
for ( m1_Iter = m1.begin( ); m1_Iter != m1.end( ); m1_Iter++ )
cout <<  m1_Iter->first<<" "<<m1_Iter->second<<endl;
}
The original map m1 is:
1 20
2 50
3 60
4 40
6 40
7 30