Find sum of all elements in a matrix except the elements in row and-or column of given cell in Python

Suppose we have a 2D matrix and a set of cell indexes. Cell indices are represented as (i, j) where i is row and j is column, now, for every given cell index (i, j), we have to find the sums of all matrix elements excluding the elements present in ith row and/or jth column.

So, if the input is like

cell indices = [(0, 0), (1, 1), (0, 1)], then the output will be [19, 14, 20]

To solve this, we will follow these steps −

• n := size of ind_arr

• ans := a new list

• for i in range 0 to n, do

  • Sum := 0

  • row := ind_arr[i, 0]

  • col := ind_arr[i, 1]

  • for j in range 0 to row count of mat, do

    • for k in range 0 to column count of map, do

      • if j is not same as row and k is not same as col, then

        • Sum := Sum + mat[j, k]

  • insert Sum at the end of ans

• return ans

Example 

Let us see the following implementation to get better understanding −

 Live Demo

def show_sums(mat, ind_arr):
   n = len(ind_arr)
   ans = []
   for i in range(0, n):
      Sum = 0
      row = ind_arr[i][0]
      col = ind_arr[i][1]
      for j in range(0, len(mat)):
         for k in range(0, len(mat[0])):
            if j != row and k != col:
               Sum += mat[j][k]
      ans.append(Sum)
   return ans
mat = [[2, 2, 3], [4, 5, 7], [6, 4, 3]]
ind_arr = [(0, 0),(1, 1),(0, 1)]
print(show_sums(mat, ind_arr))

Input

mat = [[2, 2, 3], [4, 5, 7], [6, 4, 3]] ind_arr = [(0, 0),(1, 1),(0, 1)

Output

[19, 14, 20]

Arnab Chakraborty

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Updated on: 19-Aug-2020

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