map用法

find()

find()原型：

iterator find (const key_type& k);
const_iterator find (const key_type& k) const;

需要通过iterator来查找：

#include <map>
#include <stdio.h>
#include <algorithm>
int main ()
{
  std::map<char,int> mymap;
  std::map<char,int>::iterator it;

  mymap['a']=50;
  mymap['b']=100;
  mymap['c']=150;
  mymap['d']=200;

  it = mymap.find('b');
  if (it != mymap.end())
    printf("%d\n",it->second);

  system("pause");
  return 0;
}

输出：
100

erase()

删除map中的键值–>map的大小也会减少！
c++11中的特性：

(1) iterator erase (const_iterator position);
(2) size_type erase (const key_type& k);
(3) iterator erase (const_iterator first, const_iterator last);

erase()中的参数可以是iterator、键值或者一个范围。
引用c++参考手册中的例子:

#include <iostream>
#include <map>

int main ()
{
  std::map<char,int> mymap;
  std::map<char,int>::iterator it;

  // insert some values:
  mymap['a']=10;
  mymap['b']=20;
  mymap['c']=30;
  mymap['d']=40;
  mymap['e']=50;
  mymap['f']=60;

  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

  // show content:
  for (it=mymap.begin(); it!=mymap.end(); ++it)
    std::cout << it->first << " => " << it->second << '\n';

  return 0;
}

输出：
a => 10
d => 40