diff --git a/backtracking/magic_sequence.cpp b/backtracking/magic_sequence.cpp
index 336639199..6f69492e4 100644
--- a/backtracking/magic_sequence.cpp
+++ b/backtracking/magic_sequence.cpp
@@ -1,24 +1,25 @@
 /*
- * @brief [Magic sequence](https://www.csplib.org/Problems/prob019/) implementation
+ * @brief [Magic sequence](https://www.csplib.org/Problems/prob019/)
+ * implementation
  *
  * @details Solve the magic sequence problem with a backtraking
- * 
- * "A magic sequence of length $n$ is a sequence of integers $x_0 
- *  \ldots x_{n-1}$ between $0$ and $n-1$, such that for all $i$ 
- *  in $0$ to $n-1$, the number $i$ occurs exactly $x_i$ times in 
- * the sequence. For instance, $6,2,1,0,0,0,1,0,0,0$ is a magic 
- * sequence since $0$ occurs $6$ times in it, $1$ occurs twice, etc." 
+ *
+ * "A magic sequence of length $n$ is a sequence of integers $x_0
+ *  \ldots x_{n-1}$ between $0$ and $n-1$, such that for all $i$
+ *  in $0$ to $n-1$, the number $i$ occurs exactly $x_i$ times in
+ * the sequence. For instance, $6,2,1,0,0,0,1,0,0,0$ is a magic
+ * sequence since $0$ occurs $6$ times in it, $1$ occurs twice, etc."
  * Quote of https://www.csplib.org/Problems/prob019/
  *
  * @author [Jxtopher](https://github.com/jxtopher)
  */
 
-#include <algorithm> /// for std::count
-#include <cassert>   /// for assert
-#include <iostream>  /// IO operations
-#include <list>      /// std::list
-#include <numeric>   /// std::accumulate
-#include <vector>    /// std::vector
+#include <algorithm>  /// for std::count
+#include <cassert>    /// for assert
+#include <iostream>   /// IO operations
+#include <list>       /// std::list
+#include <numeric>    /// std::accumulate
+#include <vector>     /// std::vector
 
 /**
  * @namespace
@@ -33,10 +34,9 @@ namespace backtracking {
 namespace magic_sequence {
 using sequence_t = std::vector<unsigned int>;
 
-
 /**
  * @brief print a magic sequence
- * 
+ *
  * @param s a magic sequence
  */
 void print(const sequence_t& s) {
@@ -46,11 +46,11 @@ void print(const sequence_t& s) {
 
 /**
  * @brief Check if it's a magic sequence
- * 
+ *
  * @param s a magic sequence
  * @return true if is a magic sequence
  * @return false otherwise
- * 
+ *
  */
 bool is_magic(const sequence_t& s) {
     for (unsigned int i = 0; i < s.size(); i++) {
@@ -63,12 +63,12 @@ bool is_magic(const sequence_t& s) {
 
 /**
  * @brief Filtering of sub-solutions
- * 
+ *
  * @param s a magic sequence
- * @param depth 
- * @return true if the sub-solution is valid 
+ * @param depth
+ * @return true if the sub-solution is valid
  * @return false otherwise
- * 
+ *
  */
 bool filtering(const sequence_t& s, unsigned int depth) {
     return std::accumulate(s.cbegin(), s.cbegin() + depth,
@@ -77,11 +77,11 @@ bool filtering(const sequence_t& s, unsigned int depth) {
 
 /**
  * @brief solve magic squance problem
- *  
+ *
  * @param s a magic sequence
  * @param ret list of valid magic sequences
  * @param depth depth in the tree
- * 
+ *
  */
 void solve(sequence_t* s, std::list<sequence_t>* ret, unsigned int depth = 0) {
     if (depth == s->size()) {
@@ -102,10 +102,9 @@ void solve(sequence_t* s, std::list<sequence_t>* ret, unsigned int depth = 0) {
 
 }  // namespace backtracking
 
-
 /**
  * @brief tests
- * 
+ *
  */
 static void test() {
     backtracking::magic_sequence::sequence_t s_magic = {6, 2, 1, 0, 0,