C++ map - count() Function
The C++ map::count function returns the number of occurrences of a specified key in the map container. As a map contains unique keys, hence the function returns either 1 if the key is present in the map or 0 otherwise.
Syntax
size_type count (const key_type& k) const;
size_type count (const key_type& k) const;
Parameters
k |
Specify key to search for. |
Return Value
1 if the key is present in the map, else returns 0.
Time Complexity
Logarithmic i.e, Θ(log(n)).
Example:
In the example below, the map::count function is used to check the presence of specified key in the map called MyMap.
#include <iostream> #include <map> using namespace std; int main (){ map<int, string> MyMap; map<int, string>::iterator it; MyMap[101] = "John"; MyMap[102] = "Marry"; MyMap[103] = "Kim"; MyMap[104] = "Jo"; MyMap[105] = "Ramesh"; for(int i=103; i<108; i++) { if(MyMap.count(i)==0) cout<<i<<" is not a key of MyMap.\n"; else cout<<i<<" is a key of MyMap.\n"; } return 0; }
The output of the above code will be:
103 is a key of MyMap. 104 is a key of MyMap. 105 is a key of MyMap. 106 is not a key of MyMap. 107 is not a key of MyMap.
❮ C++ <map> Library