从映射删除元素| C ++ STL
我们可以使用std::map::erase()函数来删除映射中的单个元素或元素范围。如果要删除映射中的所有元素，可以使用std::map::clear()函数。让我们详细讨论这些功能。
1.std::map::erase()函数
它将元素从映射中删除，并将映射大小减小1。
语法：
//使用迭代器擦除：
MapName.erase (it);
//其中“it”是类型映射的迭代器。
//按键擦除：
MapName.erase (key);
//按范围擦除：
MapName.erase (first,last);
//其中范围包括映射的所有元素
//在first和lasti.e[first，last）之间。程序：
#include <bits/stdc++.h>
using namespace std;
int main ()
{
map<char,int> MyMap;
//在映射中插入一些元素
MyMap['a']=1;
MyMap['b']=2;
MyMap['c']=3;
MyMap['d']=4;
MyMap['e']=5;
MyMap['f']=6;
MyMap['g']=7;
map<char,int>::iterator it;
cout<<"Elements in map : "<<endl;
for (it = MyMap.begin(); it != MyMap.end(); it++)
{
cout <<"key = "<< it->first <<" value = "<< it->second <<endl;
}
cout<<endl;
//使用键删除
MyMap.erase ('f');
//通过迭代器擦除
it=MyMap.find('e');
MyMap.erase (it);
cout<<"Elements in map after deleting f and e: "<<endl;
for (it = MyMap.begin(); it != MyMap.end(); it++)
{
cout <<"key = "<< it->first <<" value = "<< it->second <<endl;
}
cout<<endl;
//按范围擦除
//请注意，last不包含
//从a删除元素到c-
it = MyMap.find('d');
MyMap.erase ( MyMap.begin() , it );
cout<<"Elements in map after deleting a to c : "<<endl;
for (it = MyMap.begin(); it != MyMap.end(); it++)
{
cout <<"key = "<< it->first <<" value = "<< it->second <<endl;
}
return 0;
}输出结果
Elements in map : key = a value = 1 key = b value = 2 key = c value = 3 key = d value = 4 key = e value = 5 key = f value = 6 key = g value = 7 Elements in map after deleting f and e: key = a value = 1 key = b value = 2 key = c value = 3 key = d value = 4 key = g value = 7 Elements in map after deleting a to c : key = d value = 4 key = g value = 7