CODEWITHSUNDEEP
arrayslistfunctionpython-3.xdiagonal
MikeD
MikeD

Reputation: 55

Python 3 Adding Diagonals in an Array

I can't seem to find anything about adding both diagonals in a 4x4 array.

row = 4
column = 4
lis1 = [23.5, 30.1, 56.2, 11.9]
lis2 = [45.1, 8.9, 77.3, 54.1]
lis3 = [6.6, 7.7, 8.8, 2.2]
lis4 = [9.9, 8.9, 7.8, 23.6]
array = [lis1, lis2, lis3, lis4]

def diagonalSum(array):
    count = 0
    for i in range (len(array)):
        count += array[i][i]
    print ('The total of the elements in both diagonals equals  %.2f' %(count))
    return count

When I call on the function, it prints the total for lis1[0]+lis2[1]+lis3[2]+lis4[3] but I need it to also calculate the total for lis4[0]+lis3[1]+lis2[2]+lis1[3] and display the total of both diagonals. Any suggestions?

Upvotes: 0

Views: 58

Answers (1)

whwright
whwright

Reputation: 561

You are only counting the diagonal from the top left to the bottom right, in this case 0,0 1,1 2,2 3,3. You also need to count the other diagonal from the top right to the bottom left, or 0,3 1,2 2,1 3,0

To use one loop you could add another index that you increment or decrement yourself, something like this

j = len(array) - 1
for i in range(len(array)):
    # diagonal from top left to bottom right
    count += array[i][i]
    # diagonal from bottom left to top right
    count += array[j][i]
    j -= 1

Upvotes: 1

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