second commit

algorithms/CPlusPlus/README.md

@@ -211,3 +211,4 @@
 ## Backtracking
 
 - [N-Queens Problem](Backtracking/n-queens.cpp)
+- [Sudoku-Solver Problem](Backtracking/sudoku-Solver)

docs/en/Backtracking/sudoku-solver.md

@@ -0,0 +1,54 @@
+# Sudoku-Solver Problem
+
+Given a partially filled 9×9 2D array ‘grid[9][9]’, the goal is to assign digits (from 1 to 9) to the empty cells so that every row, column, and subgrid of size 3×3 contains exactly one instance of the digits from 1 to 9. 
+
+## Steps
+
+1) Create a function that checks if the given matrix is valid sudoku or not. Keep Hashmap for the row, column and boxes.
+   If any number   has a frequency greater than 1 in the hashMap return false else return true;
+2)Create a recursive function that takes a grid and the current row and column index.
+3)Check some base cases. If the index is at the end of the matrix, i.e. i=N-1 and j=N then check if the grid is safe or not,
+   if safe print the grid and return true else return false. The other base case is when the value of column is N, i.e j = N, then move to next row, i.e. i++ and j = 0.
+4)if the current index is not assigned then fill the element from 1 to 9 and recur for all 9 cases with the index of next element,
+   i.e. i, j+1. if the recursive call returns true then break the loop and return true.
+5)if the current index is assigned then call the recursive function with index of next element, i.e. i, j+1
+
+## Example
+Input:
+grid = { {3, 0, 6, 5, 0, 8, 4, 0, 0}, 
+         {5, 2, 0, 0, 0, 0, 0, 0, 0}, 
+         {0, 8, 7, 0, 0, 0, 0, 3, 1}, 
+         {0, 0, 3, 0, 1, 0, 0, 8, 0}, 
+         {9, 0, 0, 8, 6, 3, 0, 0, 5}, 
+         {0, 5, 0, 0, 9, 0, 6, 0, 0}, 
+         {1, 3, 0, 0, 0, 0, 2, 5, 0}, 
+         {0, 0, 0, 0, 0, 0, 0, 7, 4}, 
+         {0, 0, 5, 2, 0, 6, 3, 0, 0} }
+Output:
+          3 1 6 5 7 8 4 9 2
+          5 2 9 1 3 4 7 6 8
+          4 8 7 6 2 9 5 3 1
+          2 6 3 4 1 5 9 8 7
+          9 7 4 8 6 3 1 2 5
+          8 5 1 7 9 2 6 4 3
+          1 3 8 9 4 7 2 5 6
+          6 9 2 3 5 1 8 7 4
+          7 4 5 2 8 6 3 1 9
+
+
+## Time Complexity
+O(9^(n*n))
+
+## Space Complexity
+O(n*n)
+
+## Implementation
+
+- [C++](../../../algorithms/CPlusPlus/Backtracking/sudoku-Solver.cpp)
+g++ .\sudoku-Solver.cpp
+.\a.exe
+
+## Video URL
+
+[Youtube Video explaining N-queens problem](https://youtu.be/8lWxaRviJBA)
+

docs/en/README.md

@@ -23,6 +23,13 @@
 - [Binary Search](./Searching/Binary-Search.MD)
 - [Linear Search](./Searching/Linear-Search.md)
 
+## Backtracking
+
+- [n-queens](./Backtracking/N-Queens.md)
+- [sudoku-Solver](./Backtracking/sudokuSolver.cpp)
+
+
+
 ## Others
 
 [How to add new algorithm documentation?](./CONTRIBUTING.md)