moving through variables in matrix with recursion-CodePudding

I'm trying to write a function which got a kind of a matrix - a list that consists of sub-lists So I want to go through all the matrix members and print them out. Only in recursion! But I dont know how to create a good "stop conditions" for my function. So I get more numbers than I wanted.

def mission(mat):    

def move(mat, i=0, j=0 ,k=0):
    print(mat[i][j])
    if j<(len(mat[0])-1):
        move(mat,i,j 1)
    if i<(len(mat)-1):
        move(mat,i 1,0)
    
    

move(mat)


mat = [[1, 0, 0, 3, 0],
[0, 0, 2, 3, 0],
[2, 0, 0, 2, 0],
[0, 1, 2, 3, 3]]        
mission(mat)

*edit I got another question - is there a way to decrease 2 list that looks like the mat function i did here (with the same length - just different numbers) without using numpy or for ?

CodePudding user response：

You can test for end condition on function start, and check if you have already crossed the last item in the last sublist. If so, you return.

if(i == len(mat) - 1 and j == len(mat[0]) - 1):
    return

Then, you check whether you are at the last item in your current sublist, and if so, increment the sublist index i and set the item index back to 0.

if(j == len(mat[0]) - 1):
    i  = 1
    j = 0

If you are neither at the end of the whole 2d matrix (list), nor the end of any sublist, you just need to increment the item index j.

else:
    j  = 1

Then, you can safely call your function recursively. The whole code ends up looking like this.

def move(mat, i=0, j=0):
    print(mat[i][j])
    if(i == len(mat) - 1 and j == len(mat[0]) - 1):
        return
    if(j == len(mat[0]) - 1):
        i  = 1
        j = 0
    else:
        j  = 1

    move(mat, i, j)


mat = [[1, 0, 0, 3, 0],
       [0, 0, 2, 3, 0],
       [2, 0, 0, 2, 0],
       [0, 1, 2, 3, 3]]

move(mat)

Output::

CodePudding user response：

as for the move function, simply change the 2nd if to elif

def move(mat, i=0, j=0):
    print(mat[i][j])
    if j<(len(mat[0])-1):
        move(mat,i,j 1)
    elif i<(len(mat)-1):
        move(mat,i 1,0)