c++map使用方法

it2024-11-03 16

Map是c++的一个标准容器，它提供了很好一对一的关系，在一些程序中建立一个map可以起到事半功倍的效果，总结了一些map基本简单实用的操作！1. map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;

2. map添加数据；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中最简单最常用的插入添加！3，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;4,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;5,map中 swap的用法：Map中的swap不是一个容器中的元素交换，而是两个容器交换；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 mapm1.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 swapswap( 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问题：Map中的元素是自动按key升序排序,所以不能对map用sort函数：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:1 202 503 604 406 407 30请按任意键继续. . .

7， map的基本操作函数：C++ Maps是一种关联式容器，包含“关键字/值”对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trueend() 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mapupper_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

转载于:https://www.cnblogs.com/Skyxj/p/3182925.html