Find distinct elements common to all rows of a matrix in Python

PythonServer Side ProgrammingProgramming

Suppose we have a square matrix of order m x m; we have to find all the distinct elements common to all rows of the given matrix.

So, if the input is like

13215417
1532436
15215412
1526432
21942215

then the output will be [2,4,15]

To solve this, we will follow these steps −

  • Define a function sortRows() . This will take matrix

  • n := count of rows

  • for i in range 0 to n, do

    • sort the list matrix[i]

  • In the main method, do the following −

  • n := count of rows

  • sortRows(matrix)

  • current_idx := a list of size n, fill with 0

  • for i in range 0 to n, do

    • current_idx[i] := 0

  • f := 0

  • while current_idx[0] < n, do

    • value := matrix[0, current_idx[0]]

    • present := True

    • for i in range 1 to n, do

      • while (current_idx[i] < n and matrix[i][current_idx[i]] <= value, do

        • current_idx[i] := current_idx[i] + 1

      • if matrix[i, current_idx[i] - 1] is not same as value, then

        • present := False

      • if current_idx[i] is same as n, then

        • f := 1

        • come out from the loop

    • if present is non-zero, then

      • display value

    • if f is same as 1, then

      • come out from the loop

    • current_idx[0] := current_idx[0] + 1

Example

Let us see the following implementation to get better understanding −

 Live Demo

MAX = 100
def sortRows(matrix):
   n = len(matrix)
   for i in range(0, n):
      matrix[i].sort();
def find_common(matrix):
   n = len(matrix)
   sortRows(matrix)
   current_idx = [0] * n
   for i in range (0, n):
      current_idx[i] = 0
   f = 0
   while(current_idx[0] < n):
      value = matrix[0][current_idx[0]]
      present = True
      for i in range (1, n):
         while (current_idx[i] < n and matrix[i][current_idx[i]] <= value):
            current_idx[i] = current_idx[i] + 1
         if (matrix[i][current_idx[i] - 1] != value):
            present = False
         if (current_idx[i] == n):
            f = 1
            break
      if (present):
         print(value, end = ", ")
      if (f == 1):
         break
      current_idx[0] = current_idx[0] + 1

mat = [
   [13, 2, 15, 4, 17],
   [15, 3, 2, 4, 36],
   [15, 2, 15, 4, 12],
   [15, 26, 4, 3, 2],
   [2, 19, 4, 22, 15]]
find_common(mat)

Input

[[13, 2, 15, 4, 17],
[15, 3, 2, 4, 36],
[15, 2, 15, 4, 12],
[15, 26, 4, 3, 2],
[2, 19, 4, 22, 15]]

Output

2, 4, 15,
raja
Published on 25-Aug-2020 09:07:12
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