Merge pull request Bhupesh-V#480 from Manali21Gupta/pgm_clear

unordered_map clear function

unordered_map/clear.md

@@ -0,0 +1,34 @@
+# clear
+
+**Description :** This function is used to remove all elements from the container.
+
+**Example** :
+
+```cpp
+// Demonstrates clear() 
+#include <iostream>
+#include <unordered_map>
+
+int main(){
+    //declares an empty map. O(1)
+    std::unordered_map<char, int> my_map; 
+
+    // inserting in to unordered_map with O(1) time on average
+    my_map.insert({'A', 1});
+    my_map.insert({'B', 2});
+    my_map.insert({'C', 3});
+
+    //Print the size of the container
+    std::cout << "Size of unordered_map before calling clear function: " << my_map.size() << std::endl;
+
+    //Deleting all elements by calling clear function
+    my_map.clear();
+
+    //Print the size of the container
+    std::cout << "Size of unordered_map after calling clear function: " << my_map.size() << std::endl;    
+
+    return 0;
+}
+
+```
+**[Run Code](https://rextester.com/BQLV19570)**