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C++map的使用

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map的頭文件#include<map>

1. map最基本的構造函數;
map<string , int >mapstring; map<int ,string >mapint;
map<sring, char>mapstring; map< char ,string>mapchar;
map<char ,int>mapchar; map<int ,char >mapint;

2. map添加數據;//map的重復插入第二次插入無效

map<int ,string> maplive;


1.maplive.insert(pair<int,string>(102,"aclive"));
2.maplive.insert(map<int,string>::value_type(321,"hai"));
3, maplive[112]="April";//map中最簡單最常用的插入添加!
3,map中元素的查找:

find()函數返回一個叠代器指向鍵值為key的元素,如果沒找到就返回指向map尾部的叠代器。

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;
4,map中元素的刪除:
如果刪除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;
5,map中 swap的用法:
Map中的swap不是一個容器中的元素交換,而是兩個容器交換;
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;
}

6.map的sort問題:
Map中的元素是自動按key升序排序,所以不能對map用sort函數:
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
請按任意鍵繼續. . .

7, map的基本操作函數:
C++ Maps是一種關聯式容器,包含“關鍵字/值”對
begin() 返回指向map頭部的叠代器
clear() 刪除所有元素
count() 返回指定元素出現的次數
empty() 如果map為空則返回true
end() 返回指向map末尾的叠代器
equal_range() 返回特殊條目的叠代器對
erase() 刪除一個元素
find() 查找一個元素
get_allocator() 返回map的配置器
insert() 插入元素
key_comp() 返回比較元素key的函數
lower_bound() 返回鍵值>=給定元素的第一個位置
max_size() 返回可以容納的最大元素個數
rbegin() 返回一個指向map尾部的逆向叠代器
rend() 返回一個指向map頭部的逆向叠代器
size() 返回map中元素的個數
swap() 交換兩個map
upper_bound() 返回鍵值>給定元素的第一個位置
value_comp() 返回比較元素value的函數

8. map的遍歷:

map<int,string>::iterator it;

it=s1.begin();

while(it != s1.end())
{
cout << it->first << endl;
cout << it->second << endl;
it ++;
}

C++map的使用