unordered_map empty in C++ STL

unordered_map::empty() function is used to check whether container size is zero or not. If container size is zero then it return TRUE otherwise it return FALSE. Syntax: 

 unordered_map_name.empty()

Parameters: This function does not accept any parameter Return type: This function returns boolean value TRUE or FALSE. Examples: 

Input: ump = { {1, 2}, {3, 4}, {5, 6}, {7, 8}} ump.empty(); Output: False Input: ump = { }; ump.empty(); Output: True

CPP

// CPP program to illustrate
// Implementation of unordered_map empty() function
#include <bits/stdc++.h>
using namespace std;

int main()
{
    // Take any two unordered_map
    unordered_map<int, int> ump1, ump2;

    // Inserting values
    ump1[1] = 2;
    ump1[3] = 4;
    ump1[5] = 6;
    ump1[7] = 8;

    // Print the size of container
    cout << "ump1 size = " << ump1.size() << endl;
    cout << "ump2 size = " << ump2.size() << endl;

    // Running the function for ump1
    if (ump1.empty())
        cout << "True\n";
    else
        cout << "False\n";

    // Running the function for ump2
    if (ump2.empty())
        cout << "True\n";
    else
        cout << "False\n";

    // Running the function for ump1 after
    // clearing it
    ump1.clear();
    if (ump1.empty())
        cout << "True\n";
    else
        cout << "False\n";

    return 0;
}

Output:

ump1 size = 4
ump2 size = 0
False
True
True

Time complexity: O(1).

Auxiliary space: O(n). // n is the total number of elements in the unordered_map.

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