map::size() in C++ STL
Last Updated :
27 Dec, 2018
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
#include <bits/stdc++.h>
using namespace std;
int main()
{
map< int , string> map1, map2;
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" ));
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)
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