C++ map

 C++ map

[cpp] view plain copy

 

 

#include   <map>

 

1,map的初始化

 

map<char,int> map1;   //空map
map<char,int> map2(map1.begin(),map2.end()); //   取定范围初始化
map<char,int> map3(map1);   //复制 map1 的内容初始化
map<char,int> second;
second=map1;                // second now contains map1's contents
map1= map<char,int>();      // and map1 is now empty

例子：

 

#include <iostream>
#include <map>
#include <string>
using namespace std;
int main ()
{
  map<string,int> mymap;//字符串为key,int为value
  mymap["str1"] = 100;
  mymap["str2"] = 200;
  mymap["str3"] = 300;
  for (map<string,int>::iterator it=mymap.begin(); it!=mymap.end(); ++it)
     cout << it->first << " => " << it->second <<endl;
  return 0;
}

2，迭代器

 

 

for (std::map<char,int>::iterator it=mymap.begin(); it!=mymap.end(); ++it)
    std::cout << it->first << " => " << it->second << '\n';

3，容量 Capacity:

mymap.empty()  //判断是否为空
mymap.size()   //The number of elements in the container.

4， 访问元素 Element access:

 

 

mymap['a']="11";
cout <<mymap['a'] <<endl; //下标法
mymap.at('a') = 10; //at()方法

5，修改Modifiers:

 

insert()
  mymap.insert ( std::pair<char,int>('a',100) );
  std::map<char,int> anothermap;
  anothermap.insert(mymap.begin(),mymap.find('c'));  //(range insertion)
erase ()
  it=mymap.find('b');
  mymap.erase (it);                   // erasing by iterator
  mymap.erase ('c');                  // erasing by key
  it=mymap.find ('e');
  mymap.erase ( it, mymap.end() );    // erasing by range
map1.swap(map2); //交换内容，key, value类型相同，个数可以不同
clear(); //清空元素

6，操作 Operations:

find() //根据key 找元素
it = mymap.find('b');
mymap.find('a')->second
mymap.count(k); //map中有键值等于k则返回1，否者返回0