spiral matrix and prime factors exercise

python/spiral-matrix/spiral_matrix.py

@@ -0,0 +1,53 @@
+# Two lines, dude. ez.
+def spiral_matrix(size):
+    return [] if size < 1 else Matrix(size).matrix
+
+# Class for a pathfinding based spiral generation
+class Matrix:
+    def __init__(self, size):
+        self.size = size
+        self.matrix = [[None for y in range(size)] for x in range(size)]
+        self.i = 1
+        self.cur = (0, 0)
+        self.cardinals = [(0, 1), (1, 0), (-1, 0), (0, -1)]
+        self.dir_index = 0
+        self.loop()
+
+    # Loop that builds the spiral matrix
+    def loop(self):
+        # While the current number is less than the maximum number
+        while self.i < (self.size ** 2):
+            # If the next position is not valid, turn
+            if not self.valid(self.nextpos):
+                self.dir_index = (self.dir_index + 1) % 4
+            else:
+                self.access()
+                self.cur = self.nextpos
+        self.access()
+    
+    # Access a position and increment the counter
+    def access(self):
+        self.matrix[self.cur[0]][self.cur[1]] = self.i
+        self.i += 1
+
+    # Just the current direction (as an offset)
+    @property
+    def direction(self):
+        return self.cardinals[self.dir_index]
+
+    # Next position for access based on the current direction
+    @property
+    def nextpos(self):
+        return (self.cur[0] + self.direction[0], self.cur[1] + self.direction[1])
+
+    # Determine whether a position is valid to be approached
+    def valid(self, pos):
+        return self.validxy(pos[0], pos[1]) and not self.matrix[pos[0]][pos[1]]
+
+    # Determine whether a position is 
+    def validxy(self, x, y):
+        return x >= 0 and x < self.size and y >= 0 and y < self.size
+    
+    # Printable Matrix with proper character space justification
+    def __repr__(self):
+        return '\n'.join([' '.join(map(lambda item : str(item or '?').rjust(len(str(self.size ** 2))), sub)) for sub in self.matrix])