updating DIRECTORY.md

Author: Panquesito7

DIRECTORY.md

@@ -10,7 +10,7 @@
   * [Rat Maze](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/backtracking/rat_maze.cpp)
   * [Subarray Sum](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/backtracking/subarray_sum.cpp)
   * [Subset Sum](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/backtracking/subset_sum.cpp)
-  * [Sudoku Solve](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/backtracking/sudoku_solve.cpp)
+  * [Sudoku Solver](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/backtracking/sudoku_solver.cpp)
   * [Wildcard Matching](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/backtracking/wildcard_matching.cpp)
 
 ## Bit Manipulation