CODEWITHSUNDEEP
pythonlistmax
matthijs
matthijs

Reputation: 479

getting all the tiles with the maximum value in a 2d grid (a multidimensional list)

I have a 2d grid (multidimensional list) like maybe so: [[1,2,3],[1,3,3],[1,1,1]] and I want to get the positions of all elements that contain the max values, so in this case that would be: (0,3), (1,1)and(1,2).

I now have a very clumsy way which works, like this:

max_val = -999999
for i in range(board.get_dim()):
    for j in range(board.get_dim()):
        if scores[i][j] > max_val:
            max_val = scores[i][j]

max_coords = []            
for i in range(board.get_dim()):
    for j in range(board.get_dim()):
        if scores[i][j] == max_val:
            max_coords.append((i,j))

But I was hoping if someone could point me to a more concise solution?

Upvotes: 1

Views: 1025

Answers (1)

Ashwini Chaudhary
Ashwini Chaudhary

Reputation: 251011

One way is to use itertools.chain with max() to get the max value and then use a list comprehension with enumerate() to get the indices:

>>> from itertools import chain
##find the max value on a flattened version of the list 
>>> max_val = max(chain.from_iterable(lst)) 
>>> lst = [[1,2,3], [1,3,3], [1,1,1]]
>>> [(i, j) for i, x in enumerate(lst) for j, y in enumerate(x) if y == max_val]
[(0, 2), (1, 1), (1, 2)]

NumPy makes it very easy though:

>>> import numpy as np
>>> arr = np.array(lst)
>>> zip(*np.where(arr==arr.max()))
[(0, 2), (1, 1), (1, 2)]

Upvotes: 2

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