A C++ map and unordered_map are initialized to some keys and their respective mapped values.
Examples:
Input : Map : 1 -> 4, 2 -> 6, 4 -> 6 Check1 : 5, Check2 : 4 Output : 5 : Not present, 4 : Present
C++ implementation :
map
// CPP code to check if a key is present // in an unordered_map #include <bits/stdc++.h> using namespace std;
// Function to check if the key is present or not string check_key(unordered_map< int , int > m, int key)
{ // Key is not present
if (m.find(key) == m.end())
return "Not Present" ;
return "Present" ;
} // Driver int main()
{ unordered_map< int , int > m;
// Initialising keys and mapped values
m[1] = 4;
m[2] = 6;
m[4] = 6;
// Keys to be checked
int check1 = 5, check2 = 4;
// Function call
cout << check1 << ": " << check_key(m, check1) << '\n' ;
cout << check2 << ": " << check_key(m, check2);
} |
unordered_map
// CPP code to check if a // key is present in a map #include <bits/stdc++.h> using namespace std;
// Function to check if the key is present or not using count() string check_key(map< int , int > m, int key)
{ // Key is not present
if (m.count(key) == 0)
return "Not Present" ;
return "Present" ;
} // Driver int main()
{ map< int , int > m;
// Initializing keys and mapped values
m[1] = 4;
m[2] = 6;
m[4] = 6;
// Keys to be checked
int check1 = 5, check2 = 4;
// Function call
cout << check1 << ": " << check_key(m, check1) << '\n' ;
cout << check2 << ": " << check_key(m, check2);
} |
Output:
5: Not Present 4: Present
Approach 2nd:
we can also use the count function of the map in c++.
Implementation:
1. Map
C++
// CPP code to check if a key is present // in an unordered_map #include <bits/stdc++.h> using namespace std;
// Function to check if the key is present or not using count() string check_key(unordered_map< int , int > m, int key)
{ // Key is not present
if (m.count(key) == 0)
return "Not Present" ;
return "Present" ;
} // Driver int main()
{ unordered_map< int , int > m;
// Initialising keys and mapped values
m[1] = 4;
m[2] = 6;
m[4] = 6;
// Keys to be checked
int check1 = 5, check2 = 4;
// Function call
cout << check1 << ": " << check_key(m, check1) << '\n' ;
cout << check2 << ": " << check_key(m, check2);
} |
Output:
5: Not Present
4: Present
2. Unordered Map
C++
Output:
5: Not Present
4: Present