feat: Sudoku Implementation [✅] - Shuai Zhu

sudoku.go

@@ -1 +1,78 @@
 package main
+
+import (
+	"fmt"
+)
+
+const N = 9
+
+// SolveSudoku solves the Sudoku puzzle
+func SolveSudoku(grid [][]int) [][]int {
+	if solveSudokuHelper(grid) {
+		return grid
+	}
+	return nil //if the puzzle is unsolvable
+}
+
+// solveSudokuHelper is a helper function uses backtracking
+func solveSudokuHelper(grid [][]int) bool {
+	row, col := findEmptyCell(grid)
+	if row == -1 && col == -1 {
+		return true // Puzzle solved
+	}
+
+	for num := 1; num <= N; num++ {
+		if isValid(grid, row, col, num) {
+			grid[row][col] = num
+			if solveSudokuHelper(grid) {
+				return true
+			}
+			grid[row][col] = 0 // Backtrack
+		}
+	}
+	return false
+}
+
+// findEmptyCell returns the row and column of an empty cell
+func findEmptyCell(grid [][]int) (int, int) {
+	for row := 0; row < N; row++ {
+		for col := 0; col < N; col++ {
+			if grid[row][col] == 0 {
+				return row, col
+			}
+		}
+	}
+	return -1, -1
+}
+
+// isValid checks if a number can be placed in the given cell
+func isValid(grid [][]int, row, col, num int) bool {
+	// Check row and column
+	for i := 0; i < N; i++ {
+		if grid[row][i] == num || grid[i][col] == num {
+			return false
+		}
+	}
+
+	// Check 3x3 sub-grid
+	startRow := row - row%3
+	startCol := col - col%3
+	for i := 0; i < 3; i++ {
+		for j := 0; j < 3; j++ {
+			if grid[i+startRow][j+startCol] == num {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+// printGrid prints the Sudoku grid
+func printGrid(grid [][]int) {
+	for _, row := range grid {
+		for _, val := range row {
+			fmt.Printf("%d ", val)
+		}
+		fmt.Println()
+	}
+}