Program to print matrix elements in spiral order in python

Suppose we have a 2D matrix mat. We have to print the matrix elements in a spiral way. At first starting from the first row (mat[0, 0]), print the whole content and then follow the last column to print, then the last row, and so on, thus it prints the elements in a spiral fashion.

So, if the input is like

then the output will be [7, 10, 9, 1, 3, 4, 5, 11, 9, 9, 2, 9, 6, 2, 9, 2, 1, 7]

To solve this, we will follow these steps:

• d := 0
• top := 0, down := row count of matrix – 1, left := 0, right := column count of matrix - 1
• c := 0
• res := a new list
• direction := 0
• while top <= down and left <= right, do
  • if direction is same as 0, then
    • for i in range left to right + 1, do
      • insert matrix[top, i] into res
    • top := top + 1
  • if direction is same as 1, then
    • for i in range top to down + 1, do
      • insert matrix[i, right] into res
    • right := right - 1
  • if direction is same as 2, then
    • for i in range right to left - 1, decrease by 1, do
      • insert matrix[down, i] into res
    • down := down - 1
  • if direction is same as 3, then
    • for i in range down to top - 1, decrease by 1, do
      • insert matrix[i, left] into res
    • left := left + 1
• direction :=(direction + 1) mod 4
• return res

Let us see the following implementation to get better understanding:

Example

Live Demo

class Solution:    def solve(self, matrix):       d = 0       top = 0       down = len(matrix) - 1       left = 0       right = len(matrix[0]) - 1       c = 0       res = []       direction = 0       while top <= down and left <= right:          if direction == 0:             for i in range(left, right + 1):                res.append(matrix[top][i])                top += 1          if direction == 1:             for i in range(top, down + 1):                res.append(matrix[i][right])             right -= 1          if direction == 2:             for i in range(right, left - 1, -1):                res.append(matrix[down][i])             down -= 1          if direction == 3:             for i in range(down, top - 1, -1):                res.append(matrix[i][left])             left += 1          direction = (direction + 1) % 4       return res ob = Solution() matrix = [    [7, 10, 9],    [2, 9, 1],    [6, 2, 3],    [9, 1, 4],    [2, 7, 5],    [9, 9, 11] ] print(ob.solve(matrix))

Input

[     [7, 10, 9],     
[2, 9, 1],    
[6, 2, 3],     
[9, 1, 4],    
[2, 7, 5],     
[9, 9, 11]
]

Output

[7, 10, 9, 1, 3, 4, 5, 11, 9, 9, 2, 9, 6, 2, 9, 2, 1, 7]