Merge pull request Bhupesh-V#507 from Subham-Mallick/equal_range

Added equal_range in Map dir

map/README.md

@@ -21,7 +21,7 @@
 :heavy_check_mark: [size](size.md)  
 :heavy_check_mark: [swap](swap.md)  
 :heavy_check_mark: [upper_bound](upper_bound.md)  
-:x: equal_range  
+:heavy_check_mark: [equal_range](equal_range.md)  
 :x: extract  
 :x: insert_or_assign  
 :x: key_comp  

map/equal_range.md

@@ -0,0 +1,32 @@
+# equal_range
+**Description :** Returns the bounds of a range that includes all the elements in the container which have a key equivalent to k.
+
+**Example** :
+
+```cpp
+// Demonstrates equal_range
+
+#include <iostream>
+#include <map>
+
+int main (){
+	std::map<char,int> mymap;
+
+  	mymap['a']=10;
+  	mymap['b']=20;
+  	mymap['c']=30;
+
+  	std::pair<std::map<char,int>::iterator,std::map<char,int>::iterator> ret;
+  	ret = mymap.equal_range('b');
+
+  	std::cout << "lower bound points to: ";
+  	std::cout << ret.first->first << " => " << ret.first->second << '\n';
+
+  	std::cout << "upper bound points to: ";
+  	std::cout << ret.second->first << " => " << ret.second->second << '\n';
+
+  	return 0;
+}
+
+```
+**[Run Code](https://rextester.com/PDL21133)**