I can not understand why Sudoku does not fill-CodePudding

Create a program that resolves a sudoku.

A valid sudoku has only one possible solution.

I can not understand why Sudoku does not fill The code must be filled in via ASCII Parameters are taken via go run . "1..3..5.2" and so on Digits are inserted instead of dots

package main

import (
    "os"

    "github.com/01-edu/z01"
)

func printGrid(grid [9][9]rune) {
    for i := range grid {
        for j := range grid {
            z01.PrintRune(grid[i][j])
            z01.PrintRune(' ')
        }
        z01.PrintRune('\n')
    }
}

func isSafe(grid [9][9]rune, row int, col int, num rune) bool {
    for x := 0; x < len(grid); x   {
        if grid[row][x] == num || grid[x][col] == num {
            return false
        }
    }

    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
}

func Sudoku(grid [9][9]rune, row int, col int) bool {
    if col == 9 && row == 8 {
        return true
    }

    if col == 9 {
        row  
        col = 0

    }

    if grid[row][col] > '0' {
        return Sudoku(grid, row, col 1)
    }

    for num := '1'; num <= '9'; num   {
        if isSafe(grid, row, col, num) {
            grid[row][col] = num
            if Sudoku(grid, row, col 1) {
                return true
            }
        }
        grid[row][col] = '0'
    }

    return false
}

func main() {
    args := os.Args[1:]
    var grid [9][9]rune
    if len(args) == 9 {
        for i := 0; i < len(args); i   {
            for j, s := range args[i] {
                if s >= '1' && s <= '9' {
                    grid[i][j] = s
                } else {
                    grid[i][j] = '0'
                }
            }
        }
        if Sudoku(grid, 0, 0) {
            printGrid(grid)
        }

    } else {
        for _, s := range "Error" {
            z01.PrintRune(s)
        }
    }
}

I can't understand what the problem is, logically everything should be right

CodePudding user response：

your logic is right... need some corrections, I replace os.Args with args := []string because it will be painull to fill the argument of 9*9, you have to change according to your needs. I used a real sudoku puzzle and it is solved.

package main

import (
    "errors"
    "fmt"
    "os"
    "unicode/utf8"
)

func printGrid(grid [9][9]rune) {
    for i := range grid {
        for j := range grid {
            PrintRune(grid[i][j])
            PrintRune(' ')
        }
        PrintRune('\n')
    }
}

func isSafe(grid *[9][9]rune, row int, col int, num rune) bool {
    for x := 0; x < len(grid); x   {
        if grid[row][x] == num || grid[x][col] == num {
            return false
        }
    }

    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
}

func Sudoku(grid *[9][9]rune, row int, col int) bool {
    if col == 9 && row == 8 {
        return true
    }

    if col == 9 {
        row  
        col = 0

    }

    if grid[row][col] > '0' {
        return Sudoku(grid, row, col 1)
    }

    for num := '1'; num <= '9'; num   {
        if isSafe(grid, row, col, num) {
            grid[row][col] = num
            if Sudoku(grid, row, col 1) {
                return true
            }
        }
        grid[row][col] = '0'
    }

    return false
}
func PrintRune(r rune) error {
    l := utf8.RuneLen(r)
    if l == -1 {
        return errors.New("The rune is not a valid value to encode in UTF-8")
    }
    p := make([]byte, l)
    utf8.EncodeRune(p, r)
    _, err := os.Stdout.Write(p)
    return err
}
func main() {
    //args := os.Args[1:]
    args := []string{
        "2...7....",
        "...1.2734",
        "467..8..9",
        "...91...8",
        ".1..87...",
        ".862541.7",
        "..834..2.",
        "94..2.85.",
        "65..9.4.."}

    var grid [9][9]rune
    if len(args) == 9 {
        for i := 0; i < len(args[i])-1; i   {
            for j, s := range []rune(args[i]) {
                if s >= '1' && s <= '9' {
                    grid[i][j] = s
                } else {
                    grid[i][j] = '0'
                }
            }
        }
        printGrid(grid)
        fmt.Printf("\n---------\n")
        if Sudoku(&grid, 0, 0) {
            printGrid(grid)
        }

    } else {
        for _, s := range "Error" {
            PrintRune(s)
        }
    }
}

output:

2 0 0 0 7 0 0 0 0 
0 0 0 1 0 2 7 3 4 
4 6 7 0 0 8 0 0 9 
0 0 0 9 1 0 0 0 8 
0 1 0 0 8 7 0 0 0 
0 8 6 2 5 4 1 0 7 
0 0 8 3 4 0 0 2 0 
9 4 0 0 2 0 8 5 0 
         

---------
2 3 1 4 7 9 6 8 5 
8 9 5 1 6 2 7 3 4 
4 6 7 5 3 8 2 1 9 
7 2 4 9 1 3 5 6 8 
5 1 9 6 8 7 3 4 2 
3 8 6 2 5 4 1 9 7 
1 7 8 3 4 5 9 2 6 
9 4 3 7 2 6 8 5 1 
6 5 2 8 9 1 4 7 3

CodePudding user response：

os.Args[1:] evaluates to a list with one element containing your input string (represented by the literal [1..3..5.2]).

So len(args) == 9 evaluates to false, i.e. the else clause is executed.

Also, Sudoku(grid, 0, 0) will call the function Sudoku with a copy of grid. What you probably want to do, is use a pointer type instead so Sudoku can modify the content of your grid, so change the function definition to:

func Sudoku(grid *[9][9]rune, row int, col int) bool

and call the method with the address of grid (using the address-of operator &) instead of the value of grid. Lookup the difference between call by value and call by reference for more on this.