map::empty() in C++ STL
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::empty()
empty() function is used to check if the map container is empty or not.
Syntax :
mapname.empty() Parameters : No parameters are passed. Returns : True, if map is empty False, Otherwise
Examples:
Input : map mymap['a']=10; mymap['b']=20; mymap.empty(); Output : False Input : map mymap.empty(); Output : True
Errors and Exceptions
1. It has a no exception throw guarantee.
2. Shows error when a parameter is passed.
// Non Empty map example // CPP program to illustrate // Implementation of empty() function #include <iostream> #include <map> using namespace std; int main() { map< char , int > mymap; mymap[ 'a' ] = 1; mymap[ 'b' ] = 2; if (mymap.empty()) { cout << "True" ; } else { cout << "False" ; } return 0; } |
Output:
False
// Empty map example // CPP program to illustrate // Implementation of empty() function #include <iostream> #include <map> using namespace std; int main() { map< char , int > mymap; if (mymap.empty()) { cout << "True" ; } else { cout << "False" ; } return 0; } |
Output:
True
Time Complexity : O(1)
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