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Sir, I tried to write below program which solves a Sudoku puzzle using backtracking method, I saw your tutorial but I'm not getting where I have done

   h_duddu

suduko=[[0,0,0,8,0,0,1,2,0],
            [0,1,0,0,4,0,8,6,0],
            [0,0,0,0,0,1,0,0,4],
            [0,0,7,0,1,0,9,3,0],
            [1,0,4,2,9,0,0,0,0],
            [0,0,9,5,0,3,0,1,0],
            [4,6,1,0,7,0,0,5,8],
            [3,7,5,0,6,0,0,9,1],
            [2,9,8,1,0,5,0,0,0]]
def is_it_possible(i,j,num):
    #if num is 0<num<10 then check for following conditions else move to next block
    #row checking
    #coloumn checking
    #matrix checking**
    #if no number possible backtrack
    #if not move num from 1 to 9
    for k in range(0,9):
    #coloumn checking:)
        if suduko[i][k]==num:
            return False
    for k in range(0,9):
            #row checking
        if suduko[k][j]==num:
            return False
    #for checking smaller matrix we need to get i from nearby lower multiplier of 3 and higher multiplier of 3
    mat_min_i=(i//3)*3
    mat_min_j=(j//3)*3
    for x in range(mat_min_i,mat_min_i+3):
        for y in range(mat_min_j,mat_min_j+3):
            if suduko[x][y]==num:
                return False
    return True
def number_unassigned(i,j):
    num_unassigned=0
    for x in range(0,9):
        for y in range(0,9):
            if suduko[i][j]==0:
                row=i
                col=j
                num_unassigned=1
                a=[row,col,num_unassigned]
                return a
    a=[-1,-1,num_unassigned]
    return a
def suduko_filler():
    #first traverse through every box 
    #if already number exists just move to next
    #else check for numbers from 1 to 9:
    # if is_it_possible gives true move to next else
    #go to previous changed one and check for another possibility
    row=0
    col=0
    a=number_unassigned(row,col)
    row=a[0]
    col=a[1]
    if a[2]==0:
        return True
    for i in range(1,10):
        if is_it_possible(row,col,i):
            suduko[row][col]=i
            #print_suduko(suduko)
            if suduko_filler():
                return True
            suduko[row][col]=0
    return False

def print_suduko():
    for i in range(9):
        print(suduko[i])
if suduko_filler():
    print_suduko()
else:
    print("no solution")
    


Answers

  •    Aakhya Singh

    You have given wrong variable names for row and column in the number_unassigned function. The function should be written as below.

    def number_unassigned(i,j):
        num_unassigned=0
        for x in range(0,9):
            for y in range(0,9):
                if suduko[x][y]==0:
                    i=x
                    j=y
                    num_unassigned=1
                    a=[i,j,num_unassigned]
                    return a
        a=[-1,-1,num_unassigned]
        return a
    

     


    • Thanks for showing my mistakes!!!!!!
      - h_duddu

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