Create Solve_the_Sudoku.cpp

Author: Smruti2002

Backtracking/Solve_the_Sudoku.cpp

@@ -0,0 +1,116 @@
+// https://practice.geeksforgeeks.org/problems/solve-the-sudoku-1587115621/1
+
+class Solution 
+{
+    public:
+    
+    bool check(int grid[N][N],int x, int y, int k)
+    {
+        int col,row;
+        for(col = 0; col<=8; col++)
+        {
+            if(grid[x][col]==k)
+            return false;
+        }
+        for(row = 0; row<=8; row++)
+        {
+            if(grid[row][y]==k)
+            return false;
+        }
+        if(x<=2)
+            row = 0;
+        else if(x<=5)
+            row = 3;
+        else
+            row = 6;
+            
+        if(y<=2)
+            col = 0;
+        else if(y<=5)
+            col = 3;
+        else
+            col = 6;
+            
+        for(int i = row; i < (row+3); i++)
+        {
+            for(int j = col; j< (col+3); j++)
+            {
+                if(grid[i][j]==k)
+                    return false;
+            }
+        }
+        
+        return true;
+    }
+    
+    bool solve(int grid[N][N], int x, int y)
+    {
+        if(x==N-1 && y==N-1)
+        {
+            if(grid[x][y]==0)
+            {
+                for(int i = 1; i<10; i++)
+                {
+                    if(check(grid,x,y,i))
+                    {
+                        grid[x][y]=i;
+                        return true;
+                        
+                    }
+                }
+                return false;
+            }
+            return true;
+        }
+        
+        int next_row,next_col;
+        if(y==N-1)
+        {
+            next_row = x+1;
+            next_col = 0;
+        }
+        else
+        {
+            next_row = x;
+            next_col = y+1;
+        }
+        
+        if(grid[x][y]!=0)
+        {
+            return solve(grid,next_row,next_col);
+        }
+        else
+        {
+            for(int i = 1; i<10 ; i++)
+            {
+                if(check(grid,x,y,i))
+                {
+                    grid[x][y] = i;
+                    bool res = solve(grid,next_row,next_col);
+                    if(res==true)
+                        return true;
+                    grid[x][y] = 0;
+                }
+            }
+            return false;
+        }
+    }
+    
+    bool SolveSudoku(int grid[N][N])  
+    { 
+        return solve(grid,0,0);
+    }
+    
+    
+    void printGrid (int grid[N][N]) 
+    {
+        int i,j;
+        for(i=0; i<N; i++)
+        {
+            for(j=0; j<N; j++)
+            {
+                cout << grid[i][j] << " ";
+            }
+        }
+    }
+};