Common elements in all rows of a given matrix in Python

May 4, 2022

Common elements in all rows of a given matrix in Python

Here, on this page, we will discuss the program to find the Common elements in all rows of a given matrix in Python Programming language.

Common elements in all rows of the matrix

Algorithm ( Method 1 )

In this algorithm, we will check for every element in the first row, if that is present in other rows or not.

  • For checking the presence, take one variable count.
  • Now, run a loop from index 1 to M.
  • Take a variable flag =0;
  • Now, run a loop from index 0 to N, if (x==mat[i][j]) set flag =1 and break the loop.
  • After coming out from loop check if(flag==1) set, count++.
  • At last, check if count == M-1, print that value.

Time and Space Complexity :

  • Time complexity: O(M*M*N)
  • Space complexity: O(1)
Common elements in all rows of the matrix in Python

Python Code

Run 
def find(mat, N, M):
    for j in range(0, N):
        x, count = mat[0][j], 0

        for i in range(1, M):
            flag = 0
            for k in range(0, N):
                if x == mat[i][k]:
                    flag = 1
                    mat[i][k] = -1
                    break
            if flag == 1:
                count += 1
        if count == M - 1:
            print(x)


N, M = 4, 4
mat = [[10, 20, 30, 40],
       [15, 25, 35, 30],
       [27, 30, 37, 48],
       [32, 33, 39, 30]]
find(mat, N, M)

Output

30

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2 comments on “Common elements in all rows of a given matrix in Python”


  • varikutisrinivas123

    def sort(arr):
    l=[]
    for i in range(len(arr)):
    k=arr[0][i]
    for j in range(1,len(arr)):
    if k in arr[j]:
    continue
    else:
    break
    else:
    l.append(k)
    print(l)

    mat = [[10, 20, 30, 40],
    [15, 25, 35, 30],
    [27, 30, 37, 48],
    [32, 33, 39, 30]]
    sort(mat)


  • harryharish231

    r=int(input())
    c=int(input())
    matrix=[]
    sort_mat=[]
    # taking inputs in matrix
    for _ in range(r):
    row=[]
    for _ in range(c):
    row.append(int(input()))
    matrix.append(row)
    # print(matrix)
    # changing matrix into a single array (flatten)
    for i in range(r):
    for j in range(c):
    sort_mat.append(matrix[i][j])
    # print(sort_mat)
    # count the maximum times a number is repeated
    max_count=0
    for i in sort_mat:
    count=sort_mat.count(i)
    if count>max_count:
    max_count=count
    store=i
    print(i,max_count)