# 
#  Overview
In this shot, we'll learn how to use the `unordered_map::clear()` function.

# 
#  Introduction
The `unordered_map::clear()` function is available in the `<unordered_map>` header file in C++. 


The **`unordered_map::clear()`** removes all the elements from the unordered map. In other words, it empties the unordered map.

# 
#  Syntax
The syntax of the `unordered_map::clear()` function is given below.
```
void clear();
```

##
## Parameter
The `unordered_map::clear()` function does not accept any parameters.

## 
## Return value
The `unordered_map::clear()` does not return any value.

##
## Code
Let's take a look at the code.

#include <iostream>
#include <unordered_map>
using namespace std;

int main()
{
  unordered_map<int,string> umap ={
                            {12, "unordered"},
                            {16, "map"},
                            {89, "in"},
                            {66, "C++"}
                          };

  cout << "Original Map:\n";
  cout << "Size of the Map: " << umap.size() << endl;
  for(auto m: umap)
    cout << m.first << " -> " << m.second << endl;

  umap.clear();
  cout << "Original Map:\n";
  cout << "Size of the Map: " << umap.size() << endl;
  for(auto m: umap)
    cout << m.first << " -> " << m.second << endl;

  return 0;
}

# 
## Explanation

* **Lines 1–2**: We import the required header files.
* **Line 5**: We made a `main()` function.
* **Lines 7 to 12**: We initialize an unordered map with integer type keys and string type values. 

* **Line 15**: We print the current size of the map.

* **Lines 16 to 17**: We print all the key-value pairs present in the map.

* **Line 19**: We call the `unordered_map::clear()` function to empty the map.

* **Line 21**: We again print the size of the map. Now, we can see that the size is $0$.

* **Lines 22–23**: We try to print the map again, but this loop will not execute since the map is empty.


What is the unordered_map::clear() function in C++?

The unordered_map::clear() function in C++ removes all elements from an unordered map, leaving it empty.