importnumpyasnparr=[[4,5,6,8],[1,2,3,1],[7,8,9,4],[1,8,7,5]]m=np.array(arr)print(*m[0],*np.diag(np.fliplr(m))[1:-1],*m[-1])

4 5 6 8 3 8 1 8 7 5

Explanation:

• m[0] first row and np.fliplr(m) flips matrix left to right.
• np.diag(...)[1:-1] extracts reverse diagonal excluding corners and m[-1] last row.
• * unpacks all elements for printing.

Using List Comprehension

This approach combines rows and diagonals in a single list using list comprehension. It collects all required elements in order and prints them together fast and clean without extra loops.

arr=[[4,5,6,8],[1,2,3,1],[7,8,9,4],[1,8,7,5]]n=len(arr)res=[*arr[0],*[arr[i][n-i-1]foriinrange(1,n-1)],*arr[-1]]print(*res)

4 5 6 8 3 8 1 8 7 5

Explanation:

• arr[0] first row and [arr[i][n - i - 1] ...] collects reverse diagonal elements.
• arr[-1] last row and *res unpacks all values for clean printing.

Using Flattened Index Access

This method flattens the matrix into a single list and computes exact indices for the top row, diagonal, and bottom row, then prints those elements sequentially.

arr=[[4,5,6,8],[1,2,3,1],[7,8,9,4],[1,8,7,5]]n=len(arr)flt=sum(arr,[])ind=list(range(n))+[i*n+(n-i-1)foriinrange(1,n-1)]+[n*(n-1)+jforjinrange(n)]print(*[flt[i]foriinind])

4 5 6 8 3 8 1 8 7 5

Explanation:

• flt = sum(arr, []) flattens the 2D matrix and range(n) top row indices.
• Second list reverse diagonal indices and Last list bottom row indices.
• Extract and print elements using computed indices.

Using Index-Based Traversal

This method uses nested loops to traverse each required position step by step first printing the top row, then the diagonal, and finally the bottom row in order.

arr=[[4,5,6,8],[1,2,3,1],[7,8,9,4],[1,8,7,5]]n=len(arr[0])# Print first rowforjinrange(n):print(arr[0][j],end=" ")# Print opposite diagonalforiinrange(1,n-1):print(arr[i][n-i-1],end=" ")# Print last rowforjinrange(n):print(arr[n-1][j],end=" ")

4 5 6 8 3 8 1 8 7 5

Explanation:

• First for loop: arr[0][j] prints elements of the top row left to right.
• Middle loop: for each row i from 1 to n-2, arr[i][n-i-1] computes the column index for the opposite diagonal and prints that element.
• Last for loop: arr[n-1][j] prints all elements of the bottom row.