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.
map::size()
In C++, size() function is used to return the total number of elements present in the map.
Syntax:
map_name.size()
Return Value: It returns the number of elements present in the map.
Examples:
Input : map1 = { {1, "India"}, {2, "Nepal"}, {3, "Sri Lanka"}, {4, "Myanmar"} } map1.size(); Output: 4 Input : map2 = {}; map2.size(); Output: 0
// C++ program to illustrate // implementation of size() function #include <bits/stdc++.h> using namespace std;
int main()
{ // Take any two maps
map< int , string> map1, map2;
// Inserting values
map1.insert(make_pair(1, "India" ));
map1.insert(make_pair(2, "Nepal" ));
map1.insert(make_pair(3, "Sri Lanka" ));
map1.insert(make_pair(4, "Myanmar" ));
// Printing the size
cout << "map1 size: " << map1.size();
cout << endl;
cout << "map2 size: " << map2.size();
return 0;
} |
Output:
map1 size: 4 map2 size: 0
Time complexity: Constant i.e. O(1)