[LeetCode] 59. Spiral Matrix II

Problem : https://leetcode.com/problems/spiral-matrix-ii/

Use FSM to simulate the process for filling numbers. Be careful, it must break the loop immediately when i >= n * n.

class Solution(object):
    def generateMatrix(self, n):
        """
        :type n: int
        :rtype: List[List[int]]
        """
        
        board = [[0] * n for _ in range(n)]
        
        i = 1
        board[0][0] = 1
        
        y, x = 0, 0
        padding_y, padding_x = 0, 0
        
        state = 'right'
        
        while True:
            if state == 'right':
                if x + 1 >= n - padding_x:
                    state = 'down'
                else:
                    x += 1
                    i += 1
                    board[y][x] = i
            
            elif state == 'down':
                if y + 1 >= n - padding_y:
                    state = 'left'
                else:
                    y += 1
                    i += 1
                    board[y][x] = i
                    
            elif state == 'left':
                if x - 1 < padding_x:
                    state = 'up'
                    padding_y += 1
                else:
                    x -= 1
                    i += 1
                    board[y][x] = i
                    
            elif state == 'up':
                if y - 1 < padding_y:
                    state = 'right'
                    padding_x +=1 
                else:
                    y -= 1
                    i += 1
                    board[y][x] = i
                    
            if i >= n * n:
                break
                    
        return board