September Morn Update

Task/Zig-zag-matrix/Python/zig-zag-matrix-1.py

@@ -1,13 +1,22 @@
 def zigzag(n):
-    indexorder = sorted(((x,y) for x in range(n) for y in range(n)),
-                    key = lambda (x,y): (x+y, -y if (x+y) % 2 else y) )
-    return {index: n for n,index in enumerate(indexorder)}
+    '''zigzag rows'''
+    def compare(xy):
+        x, y = xy
+        return (x + y, -y if (x + y) % 2 else y)
+    xs = range(n)
+    return {index: n for n, index in enumerate(sorted(
+        ((x, y) for x in xs for y in xs),
+        key=compare
+    ))}
+
 
 def printzz(myarray):
-    n = int(len(myarray)** 0.5 +0.5)
-    for x in range(n):
-        for y in range(n):
-                print "%2i" % myarray[(x,y)],
-        print
+    '''show zigzag rows as lines'''
+    n = int(len(myarray) ** 0.5 + 0.5)
+    xs = range(n)
+    print('\n'.join(
+        [''.join("%3i" % myarray[(x, y)] for x in xs) for y in xs]
+    ))
+
 
 printzz(zigzag(6))

Task/Zig-zag-matrix/Python/zig-zag-matrix-2.py

@@ -1,18 +1,33 @@
-def zigzag(n):
-    def move(i, j):
-        if j < (n - 1):
-            return max(0, i-1), j+1
-        else:
-            return i+1, j
-    a = [[0] * n for _ in xrange(n)]
+# pylint: disable=invalid-name
+# pylint: disable=unused-argument
+"ZigZag iterator."
+import sys
+
+if sys.version_info[0] >= 3:
+    xrange = range
+
+def move(x, y, columns, rows):
+    "Tells us what to do next with x and y."
+    if y < (rows - 1):
+        return max(0, x-1), y+1
+    return x+1, y
+
+def zigzag(rows, columns):
+    "ZigZag iterator, yields indices."
     x, y = 0, 0
-    for v in xrange(n * n):
-        a[y][x] = v
+    size = rows * columns
+    for _ in xrange(size):
+        yield y, x
         if (x + y) & 1:
-            x, y = move(x, y)
+            x, y = move(x, y, columns, rows)
         else:
-            y, x = move(y, x)
-    return a
+            y, x = move(y, x, rows, columns)
+
+# test code
+i, rows, cols = 0, 5, 5
+mat = [[0 for x in range(cols)] for y in range(rows)]
+for (y, x) in zigzag(rows, cols):
+    mat[y][x], i = i, i + 1
 
 from pprint import pprint
-pprint(zigzag(5))
+pprint(mat)