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Check if a key is present in a C++ map or unordered_map

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 a map
#include <bits/stdc++.h>
using namespace std;
  
// Function to check if the key is present or not
string check_key(map<int, int> m, int key)
{
    // Key is not present
    if (m.find(key) == m.end())
        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 ce checked
    int check1 = 5, check2 = 4;
  
    // Function call
    cout << check1 << ": " << check_key(m, check1) << ' ';
    cout << check2 << ": " << check_key(m, check2);
}

unordered_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 ce checked
    int check1 = 5, check2 = 4;
  
    // Function call
    cout << check1 << ": " << check_key(m, check1) << ' ';
    cout << check2 << ": " << check_key(m, check2);
}


Output:

5: Not Present
4: Present

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.



This article is attributed to GeeksforGeeks.org

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