Added backtracking sudoku solver solution

sudoku.go

@@ -1 +1,80 @@
 package main
+
+func SolveSudoku(board [9][9]int) [9][9]int {
+	for i := 0; i < 9; i++ {
+		for j := 0; j < 9; j++ {
+			if board[i][j] == 0 {
+				for digit := 9; digit >= 1; digit-- {
+					board[i][j] = digit
+					if CheckBoardValidity(board) {
+						if IsBoardComplete(board) {
+							return board
+						} else {
+							SolveSudoku(board)
+						}
+					}
+					board[i][j] = 0
+				}
+				return [9][9]int{} // If no solution found, return an empty board
+			}
+		}
+	}
+	return board
+}
+
+func CheckBoardValidity(board [9][9]int) bool {
+	// Check duplicates by row
+	for row := 0; row < 9; row++ {
+		rowMap := make(map[int]int)
+		for col := 0; col < 9; col++ {
+			if rowMap[board[row][col]] == 1 {
+				return false
+			} else {
+				rowMap[board[row][col]] = 1
+			}
+		}
+	}
+
+	// Check duplicates by column
+	for col := 0; col < 9; col++ {
+		colMap := make(map[int]int)
+		for row := 0; row < 9; row++ {
+			if colMap[board[row][col]] == 1 {
+				return false
+			} else {
+				colMap[board[row][col]] = 1
+			}
+		}
+	}
+
+	// Check duplicates in 3x3 sections
+	for i := 0; i < 9; i += 3 {
+		for j := 0; j < 9; j += 3 {
+			threeByThreeMap := make(map[int]int)
+			for row := i; row < i+3; row++ {
+				for col := j; col < j+3; col++ {
+					if board[row][col] != 0 {
+						if threeByThreeMap[board[row][col]] == 1 {
+							return false
+						} else {
+							threeByThreeMap[board[row][col]] = 1
+						}
+					}
+				}
+			}
+		}
+	}
+
+	return true
+}
+
+func IsBoardComplete(board [9][9]int) bool {
+	for i := 0; i < 9; i++ {
+		for j := 0; j < 9; j++ {
+			if board[i][j] == 0 {
+				return false
+			}
+		}
+	}
+	return true
+}