Explaining the fill_n function

algorithm/README.md

@@ -15,6 +15,7 @@
 :heavy_check_mark: [equal](equal.md)  
 :heavy_check_mark: [equal_range](equal_range.md)  
 :heavy_check_mark: [fill](fill.md)  
+:heavy_check_mark: [fill_n](fill_n.md)
 :heavy_check_mark: [find](find.md)  
 :heavy_check_mark: [find_first_of](find_first_of.md)  
 :heavy_check_mark: [find_if](find_if.md)  
@@ -72,7 +73,6 @@
 :heavy_check_mark: [upper_bound](upper_bound.md)  
 :x: destroy  
 :x: exclusive_scan  
-:x: fill_n  
 :x: find_end  
 :x: generate_n  
 :x: inclusive_scan  

algorithm/fill_n.md

@@ -0,0 +1,35 @@
+# fill_n
+
+**Description** : Sets a number of elements of a range (i.e, vector) to a value.
+The function takes 3 arguments. The iterator of the range, the number of elements
+to set starting from the iterator's first element and the new value.
+
+**Example** :
+```cpp
+    #include <iostream>
+    #include <vector>
+    #include <algorithm>
+
+    void print_vector(const std::vector<int> &v) {
+        // iterate through v and print its elements
+        for(auto &elem:v) {
+            std::cout << elem << " ";
+        }
+        std::cout<<std::endl;
+    }
+
+    int main() {
+        std::vector<int> v = {1,1,1,1,1,1,1,1};
+
+        std::cout << "Before fill_n: ";
+        print_vector(v);
+
+        // set the first half of v's elements to zero
+        std::fill_n(v.begin(), v.size()/2, 0);
+
+        std::cout << "After  fill_n: ";
+        print_vector(v);
+        return 0;
+    }
+```
+**[Run Code](https://rextester.com/CIZQZ21473)**

snippets/algorithm/fill_n.cpp

@@ -0,0 +1,32 @@
+/*
+   Author : Klajdi Bodurri
+   Date : 08/01/2020
+   Time : 14:00
+   Description : Show an example of fill_n
+*/
+
+#include <iostream>
+#include <vector>
+#include <algorithm>
+
+void print_vector(const std::vector<int> &v) {
+    // iterate through v and print its elements
+    for(auto &elem:v) {
+        std::cout << elem << " ";
+    }
+    std::cout<<std::endl;
+}
+
+int main() {
+    std::vector<int> v = {1,1,1,1,1,1,1,1};
+
+    std::cout << "Before fill_n: ";
+    print_vector(v);
+
+    // set the first half of v's elements to zero
+    std::fill_n(v.begin(), v.size()/2, 0);
+
+    std::cout << "After  fill_n: ";
+    print_vector(v);
+    return 0;
+}