Take indices of non zero elements of matrix

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Hi, I create matrix "adjacency_matrix" with following code:

Python

n = int(input()) # Initialize matrix

adjacency_matrix = []

# For user input

for i in range(n):

a =[]

for j in range(n):

a.append(int(input()))

adjacency_matrix.append(a)

I want to save indices of non zero elements of above matrix.

for example n = 3;

Python

adjacency_matrix =

2 3 0

0 0 1

1 5 0

I want to save rows of non zero element in "li_r":

Python

li_r = [0 0 1 2 2]

I want to save columns of non zero element in "li_c":

Python

li_c = [0 1 2 0 1]

My Question is: Is this code is true?

Python

for i in range(n):

li_r = [];

li_c = []

for j in range(n):

if adjacency_matrix[i-1][j-1]!=0:

li_r.append(i-1)

li_c.append(j-1)

What I have tried:

I write that code, by it's not work.

Posted 15-Jun-22 16:35pm

niksirat2030

Updated 15-Jun-22 20:30pm

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1 solution

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This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

CPallini · Answer 1 · 2022-06-15T20:29:00

Try the following code

Python

n=3
adjacency_matrix =[ [2, 3, 0] , [0, 0, 1] , [1, 5, 0] ]

li_r = []
li_c = []
for i in range(n):
  for j in range(n):
    if adjacency_matrix[i][j]!=0:
      li_r.append(i)
      li_c.append(j)

print(li_r)
print(li_c)

You may also use the more concise, but less efficient

Python

n=3
adjacency_matrix =[ [2, 3, 0] , [0, 0, 1] , [1, 5, 0] ]

li_r = [r for r in range(n) for c in range(n) if adjacency_matrix[r][c] != 0]
li_c = [c for r in range(n) for c in range(n) if adjacency_matrix[r][c] != 0]

print(li_r)
print(li_c)

Take indices of non zero elements of matrix

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Take indices of non zero elements of matrix

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