Problems counting zeroes standing at the beginning of rows in a matrix

February 7, 2022

In Python I have tried to use the code below to fill a list with occurences of zeroes in rows of a matrix. These 0 must stand before all the non zero-numbers: for example in a row like [0,0,3,0] I would count only the first two zeroes.

occurence_of_zeroes=[0]*dim
for i in range(dim):
   for j in range(dim):
      while matrix[i][j]==0:
         occurence_of_zeroes[i]=occurence_of_zeroes[i]+1
   print("In row ",i+1," there are ",occurence_of_zeroes[i]," zeroes at the beginning")
print("Is this working?")

when I try to execute the code with previously defined dim and matrix, the console never spits out the result and freezes. Why?

>Solution :

The problem is that you don’t exit the while loop to increment j. Here’s a fix to your code.

occurence_of_zeroes=[0]*dim
for i in range(dim):
    for j in range(dim):
        if matrix[i][j]!=0:
            break    
        occurence_of_zeroes[i]=occurence_of_zeroes[i]+1
    print("In row ",i+1," there are ",occurence_of_zeroes[i]," zeroes at the beginning")
print("Is this working?")