""" This program print the matrix in spiral form. This problem has been solved through recursive way. Matrix must satisfy below conditions i) matrix should be only one or two dimensional ii) number of column of all rows should be equal """ def check_matrix(matrix: list[list[int]]) -> bool: # must be matrix = [list(row) for row in matrix] if matrix and isinstance(matrix, list): if isinstance(matrix[0], list): prev_len = 0 for row in matrix: if prev_len == 0: prev_len = len(row) result = True else: result = prev_len == len(row) else: result = True else: result = False return result def spiral_print_clockwise(a: list[list[int]]) -> None: """ >>> spiral_print_clockwise([[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]]) 1 2 3 4 8 12 11 10 9 5 6 7 """ if check_matrix(a) and len(a) > 0: a = [list(row) for row in a] mat_row = len(a) if isinstance(a[0], list): mat_col = len(a[0]) else: for dat in a: print(dat) return # horizotal printing increasing for i in range(mat_col): print(a[0][i]) # vertical printing down for i in range(1, mat_row): print(a[i][mat_col - 1]) # horizotal printing decreasing if mat_row > 1: for i in range(mat_col - 2, -1, -1): print(a[mat_row - 1][i]) # vertical printing up for i in range(mat_row - 2, 0, -1): print(a[i][0]) remain_mat = [row[1 : mat_col - 1] for row in a[1 : mat_row - 1]] if len(remain_mat) > 0: spiral_print_clockwise(remain_mat) else: return else: print("Not a valid matrix") return # Other Easy to understand Approach def spiral_traversal(matrix: list[list]) -> list[int]: """ >>> spiral_traversal([[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]]) [1, 2, 3, 4, 8, 12, 11, 10, 9, 5, 6, 7] Example: matrix = [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]] Algorithm: Step 1. first pop the 0 index list. (which is [1,2,3,4] and concatenate the output of [step 2]) Step 2. Now perform matrix’s Transpose operation (Change rows to column and vice versa) and reverse the resultant matrix. Step 3. Pass the output of [2nd step], to same recursive function till base case hits. Dry Run: Stage 1. [1, 2, 3, 4] + spiral_traversal([ [8, 12], [7, 11], [6, 10], [5, 9]] ]) Stage 2. [1, 2, 3, 4, 8, 12] + spiral_traversal([ [11, 10, 9], [7, 6, 5] ]) Stage 3. [1, 2, 3, 4, 8, 12, 11, 10, 9] + spiral_traversal([ [5], [6], [7] ]) Stage 4. [1, 2, 3, 4, 8, 12, 11, 10, 9, 5] + spiral_traversal([ [5], [6], [7] ]) Stage 5. [1, 2, 3, 4, 8, 12, 11, 10, 9, 5] + spiral_traversal([[6, 7]]) Stage 6. [1, 2, 3, 4, 8, 12, 11, 10, 9, 5, 6, 7] + spiral_traversal([]) """ if matrix: return list(matrix.pop(0)) + spiral_traversal( [list(row) for row in zip(*matrix)][::-1] ) else: return [] # driver code if __name__ == "__main__": import doctest doctest.testmod() a = [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]] spiral_print_clockwise(a)