Merge pull request #557 from MrLakshay/patch-1

Adding sudoku solver

Author: Sirajmolla

C++/Sudoku.cpp

@@ -0,0 +1,91 @@
+/*
+ Author : Lakshay Goel
+ Github : https://github.com/MrLakshay
+ File : Sudoku Solver
+ Time Complexity: O(n*n)
+ Algorithm used: Backtracking
+*/
+#include <iostream>
+#include <math.h>
+using namespace std;
+bool isSafe(int board[][9], int i, int j, int no, int n)
+{
+    // row and col mai nhi hona chahiye
+    for (int k = 0; k < n; k++)
+    {
+        if (board[i][k] == no || board[k][j] == no)
+        {
+            return false;
+        }
+    }
+
+    // daba checking idhar hogi
+    n = sqrt(n);
+    int si = (i / n) * n;
+    int sj = (j / n) * n;
+    for (int k = si; k < si + n; k++)
+    {
+        for (int l = sj; l < sj + n; l++)
+        {
+            if (board[k][l] == no)
+            {
+                return false;
+            }
+        }
+    }
+    return true;
+}
+bool SudokuSolver(int board[][9], int i, int j, int n)
+{
+    // base case
+    if (i == n)
+    {
+        for (int l = 0; l < 9; l++)
+        {
+            for (int m = 0; m < 9; m++)
+            {
+                cout << board[l][m] << " ";
+            }
+            cout << endl;
+        }
+        return true;
+    }
+    // recursive case
+    if (j == n)
+    {
+        return SudokuSolver(board, i + 1, 0, n); // agar column n pee pohoch jaye toh niche kaar doo
+    }
+    if (board[i][j] != 0)
+    {
+        return SudokuSolver(board, i, j + 1, n);
+    }
+    for (int no = 1; no < 10; no++)
+    {
+        if (isSafe(board, i, j, no, n))
+        {
+            board[i][j] = no;
+            bool baakisolve = SudokuSolver(board, i, j + 1, n);
+            if (baakisolve)
+            {
+                return true;
+            }
+            board[i][j] = 0;
+        }
+    }
+    return false;
+}
+int main()
+{
+    int sudoku[9][9] = {
+        {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}};
+    SudokuSolver(sudoku, 0, 0, 9);
+    return 0;
+}