Write a recursive function column2list_rec ( grid , n ), where grid is a list of

Question

Write a recursive function column2list_rec(grid, n), where gridis a list of lists and n is an integer, that returns a list consisting of the element at position n of each row of grid.

You can assume that 0 ? n < len(r) for each row (i.e., element) of grid.

Programming Requirements

Solve this problem using recursion. You are allowed to use onlythe following programming constructs:

if statements;

return statements;

assignment;

recursive function calls (but not to helper functions);

comparison operations (==, !=, etc.);

list indexing and slicing;

list concatenation/extension.

Solutions that go outside these constructs, e.g., by using for/while loops or list comprehensions, will not get credit.

Explanation / Answer

# helper function def column2list_rec_helper(grid, n, i): if i == len(grid): # base case is when i is len(grid) return [] # return empty list else: return [grid[i][n]] + column2list_rec_helper(grid, n, i + 1) # append diagonal element at row i column i to result to recursive call def column2list_rec(grid, n): return column2list_rec_helper(grid, n, 0) print(column2list_rec([[1, 2, 3], [4, 5, 6], [7, 8, 9]], 2))

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