Maps are associative containers that store elements in a mapped fashion. Each element has a key value and a mapped value. No two mapped values can have same key values.
Some basic functions associated with Map:
begin() – Returns an iterator to the first element in the map
end() – Returns an iterator to the theoretical element that follows last element in the map
size() – Returns the number of elements in the map
max_size() – Returns the maximum number of elements that the map can hold
empty() – Returns whether the map is empty
pair insert(keyvalue, mapvalue) – Adds a new element to the map
erase(iterator position) – Removes the element at the position pointed by the iterator
erase(const g)– Removes the key value ‘g’ from the map
clear() – Removes all the elements from the map
#include <iostream>
#include <iterator>
#include <map>
using namespace std;
int main()
{
// empty map container
map<int, int> gquiz1;
// insert elements in random order
gquiz1.insert(pair<int, int>(1, 40));
gquiz1.insert(pair<int, int>(2, 30));
gquiz1.insert(pair<int, int>(3, 60));
gquiz1.insert(pair<int, int>(4, 20));
gquiz1.insert(pair<int, int>(5, 50));
gquiz1.insert(pair<int, int>(6, 50));
gquiz1.insert(pair<int, int>(7, 10));
// printing map gquiz1
map<int, int>::iterator itr;
cout << "\nThe map gquiz1 is : \n";
cout << "\tKEY\tELEMENT\n";
for (itr = gquiz1.begin(); itr != gquiz1.end(); ++itr) {
cout << '\t' << itr->first
<< '\t' << itr->second << '\n';
}
cout << endl;
// assigning the elements from gquiz1 to gquiz2
map<int, int> gquiz2(gquiz1.begin(), gquiz1.end());
// print all elements of the map gquiz2
cout << "\nThe map gquiz2 after"
<< " assign from gquiz1 is : \n";
cout << "\tKEY\tELEMENT\n";
for (itr = gquiz2.begin(); itr != gquiz2.end(); ++itr) {
cout << '\t' << itr->first
<< '\t' << itr->second << '\n';
}
cout << endl;
// remove all elements up to
// element with key=3 in gquiz2
cout << "\ngquiz2 after removal of"
" elements less than key=3 : \n";
cout << "\tKEY\tELEMENT\n";
gquiz2.erase(gquiz2.begin(), gquiz2.find(3));
for (itr = gquiz2.begin(); itr != gquiz2.end(); ++itr) {
cout << '\t' << itr->first
<< '\t' << itr->second << '\n';
}
// remove all elements with key = 4
int num;
num = gquiz2.erase(4);
cout << "\ngquiz2.erase(4) : ";
cout << num << " removed \n";
cout << "\tKEY\tELEMENT\n";
for (itr = gquiz2.begin(); itr != gquiz2.end(); ++itr) {
cout << '\t' << itr->first
<< '\t' << itr->second << '\n';
}
cout << endl;
// lower bound and upper bound for map gquiz1 key = 5
cout << "gquiz1.lower_bound(5) : "
<< "\tKEY = ";
cout << gquiz1.lower_bound(5)->first << '\t';
cout << "\tELEMENT = "
<< gquiz1.lower_bound(5)->second << endl;
cout << "gquiz1.upper_bound(5) : "
<< "\tKEY = ";
cout << gquiz1.upper_bound(5)->first << '\t';
cout << "\tELEMENT = "
<< gquiz1.upper_bound(5)->second << endl;
return 0;
}
The map gquiz1 is :
KEY ELEMENT
1 40
2 30
3 60
4 20
5 50
6 50
7 10
The map gquiz2 after assign from gquiz1 is :
KEY ELEMENT
1 40
2 30
3 60
4 20
5 50
6 50
7 10
gquiz2 after removal of elements less than key=3 :
KEY ELEMENT
3 60
4 20
5 50
6 50
7 10
gquiz2.erase(4) : 1 removed
KEY ELEMENT
3 60
5 50
6 50
7 10
gquiz1.lower_bound(5) : KEY = 5 ELEMENT = 50
gquiz1.upper_bound(5) : KEY = 6 ELEMENT = 50
Program ended with exit code: 0