Standard library map set delete
Delete operation
The map is as follows:
map<int, size_t> cnt{{2,22}, {3,33}, {1,11}, {4,44};Delete method:
| Delete operation type | Function description |
|---|---|
| cnt.erase(3); | Delete the element with key 3 and return the number of deleted elements |
| cnt.erase(p); | P is the iterator, delete the element pointed by P, and return the iterator of the element after p |
| cnt.erase(b, e); | b. E is the iterator, delete the elements of the range represented by B and E, and return e |
Note: when using the iterator to delete, the map, set and list iterators do not support the addition and subtraction operations, but they can + + -.
map<int, int>::const_iterator it = mp.cbegin(); auto it2 = it + 2;//NG ++it;//OK
Small example:
#include <iostream>
#include <map>
#include <set>
#include <vector>
#include <list>
#include <algorithm>
using namespace std;
int main(){
map<int , int> mp{{2,22},{3,33},{1,11},{4,44}};
for(auto const &s : mp){
cout << s.first << "," << s.second << endl;
}
cout << "-----------------" << endl;
map<int, int>::const_iterator it = mp.cbegin();
//map,set,list iterators do not support addition and subtraction operations, but can be + +, -.
//auto it2 = it + 2;//NG
auto it2 = mp.find(2);
auto rt2 = mp.erase(it, it2);//Delete 1,rt2 points to (2,22)
cout << rt2->first << ":" << rt2->second << endl;
auto rt1 = mp.erase(it2);//Delete 2
cout << rt1->first << ":" << rt1->second << endl;
auto rt = mp.erase(3);//Delete 3, return value is 1 or 0, because 3 exists, return 1
for(auto const &s : mp){
cout << s.first << "," << s.second << endl;
}
}