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.

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// 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;
}

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Output:

False
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// 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;
}

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Output:

True

Time Complexity : O(1)



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