SUDOKU.cpp

SUDOKU.cpp

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+#include <bits/stdc++.h> 
+using namespace std; 
+
+#define UNASSIGNED 0 
+#define N 9 
+
+bool FindUnassignedLocation(int grid[N][N], int &row, int &col); 
+
+bool isSafe(int grid[N][N], int row, int col, int num); 
+
+bool SolveSudoku(int grid[N][N]) 
+{ 
+	int row, col; 
+	if (!FindUnassignedLocation(grid, row, col)) 
+	return true; 
+
+	for (int num = 1; num <= 9; num++) 
+	{ 
+		if (isSafe(grid, row, col, num)) 
+		{ 
+			grid[row][col] = num; 
+
+			if (SolveSudoku(grid)) 
+				return true; 
+
+			grid[row][col] = UNASSIGNED; 
+		} 
+	} 
+	return false; 
+} 
+
+bool FindUnassignedLocation(int grid[N][N], 
+							int &row, int &col) 
+{ 
+	for (row = 0; row < N; row++) 
+		for (col = 0; col < N; col++) 
+			if (grid[row][col] == UNASSIGNED) 
+				return true; 
+	return false; 
+} 
+
+
+bool UsedInRow(int grid[N][N], int row, int num) 
+{ 
+	for (int col = 0; col < N; col++) 
+		if (grid[row][col] == num) 
+			return true; 
+	return false; 
+} 
+
+
+bool UsedInCol(int grid[N][N], int col, int num) 
+{ 
+	for (int row = 0; row < N; row++) 
+		if (grid[row][col] == num) 
+			return true; 
+	return false; 
+} 
+
+
+bool UsedInBox(int grid[N][N], int boxStartRow, int boxStartCol, int num) 
+{ 
+	for (int row = 0; row < 3; row++) 
+		for (int col = 0; col < 3; col++) 
+			if (grid[row + boxStartRow] 
+					[col + boxStartCol] == num) 
+				return true; 
+	return false; 
+} 
+
+bool isSafe(int grid[N][N], int row, int col, int num) 
+{ 
+
+	return !UsedInRow(grid, row, num) && 
+		!UsedInCol(grid, col, num) && 
+		!UsedInBox(grid, row - row % 3 , 
+					col - col % 3, num) && 
+			grid[row][col] == UNASSIGNED; 
+} 
+
+
+void printGrid(int grid[N][N]) 
+{ 
+	cout<<endl;
+	for (int row = 0; row < N; row++) 
+	{ 
+	for (int col = 0; col < N; col++) 
+			cout << grid[row][col] << " "; 
+		cout << endl; 
+	} 
+} 
+
+int main() 
+{ 
+
+	int grid[N][N] = {{0}};
+	for(int i=0;i<N;i++)
+	{
+		for(int j=0;j<N;j++)
+		cin>>grid[i][j];
+	}
+	if (SolveSudoku(grid) == true) 
+		printGrid(grid); 
+	else
+		cout << "No solution exists"; 
+
+	return 0; 
+} 
+