map::erase
Removes an element or a range of elements in a map from specified positions or removes elements that match a specified key.
iterator erase(
iterator _Where
);
iterator erase(
iterator _First,
iterator _Last
);
size_type erase(
const key_type& _Key
);
Parameters
_Where
Position of the element to be removed from the map._First
Position of the first element removed from the map._Last
Position just beyond the last element removed from the map._Key
The key value of the elements to be removed from the map.
Return Value
For the first two member functions, a bidirectional iterator that designates the first element remaining beyond any elements removed, or a pointer to the end of the map if no such element exists.
注意
This return type does not conform to the C++ standard.
For the third member function, returns the number of elements that have been removed from the map.
Remarks
In some instances, this method might throw an out_of_range exception. This behavior does not conform to the C++ standard.
Example
When compiling this example with the /Wp64 flag or on a 64-bit platform, compiler warning C4267 will be generated. For more information on this warning, see Compiler Warning (level 3) C4267.
// map_erase.cpp
// compile with: /EHsc
#include <map>
#include <iostream>
int main()
{
using namespace std;
map<int, int> m1, m2, m3;
map<int, int>::iterator pIter, Iter1, Iter2;
int i;
map<int, int>::size_type n;
typedef pair<int, int> Int_Pair;
for (i = 1; i < 5; i++)
{
m1.insert(Int_Pair(i, i));
m2.insert(Int_Pair(i, i*i));
m3.insert(Int_Pair(i, i-1));
}
// The 1st member function removes an element at a given position
Iter1 = ++m1.begin();
m1.erase(Iter1);
cout << "After the 2nd element is deleted, the map m1 is:";
for (pIter = m1.begin(); pIter != m1.end(); pIter++)
cout << " " << pIter->second;
cout << "." << endl;
// The 2nd member function removes elements
// in the range [_First, _Last)
Iter1 = ++m2.begin();
Iter2 = --m2.end();
m2.erase(Iter1, Iter2);
cout << "After the middle two elements are deleted,"
<< " the map m2 is:";
for (pIter = m2.begin(); pIter != m2.end(); pIter++)
cout << " " << pIter->second;
cout << "." << endl;
// The 3rd member function removes elements with a given _Key
n = m3.erase(2);
cout << "After the element with a key of 2 is deleted,\n"
<< "the map m3 is:";
for (pIter = m3.begin(); pIter != m3.end(); pIter++)
cout << " " << pIter->second;
cout << "." << endl;
// The 3rd member function returns the number of elements removed
cout << "The number of elements removed from m3 is: "
<< n << "." << endl;
// The dereferenced iterator can also be used to specify a key
Iter1 = ++m3.begin();
m3.erase(Iter1);
cout << "After another element with a key equal to that"
<< endl;
cout << "of the 2nd element is deleted, "
<< "the map m3 is:";
for (pIter = m3.begin(); pIter != m3.end(); pIter++)
cout << " " << pIter->second;
cout << "." << endl;
}
After the 2nd element is deleted, the map m1 is: 1 3 4.
After the middle two elements are deleted, the map m2 is: 1 16.
After the element with a key of 2 is deleted,
the map m3 is: 0 2 3.
The number of elements removed from m3 is: 1.
After another element with a key equal to that
of the 2nd element is deleted, the map m3 is: 0 3.
Requirements
Header: <map>
Namespace: std