Merge pull request keon#95 from ofek/master

add matrix transformations

README.md

@@ -109,6 +109,7 @@ Minimal and clean example implementations of data structures and algorithms in P
     - [pythagoras](math/pythagoras.py)
 - [matrix](matrix)
     - [matrix_rotation.txt](matrix/matrix_rotation.txt)
+    - [copy_transform](matrix/copy_transform.py)
     - [bomb_enemy](matrix/bomb_enemy.py)
     - [rotate_image](matrix/rotate_image.py)
     - [sparse_dot_vector](matrix/sparse_dot_vector.py)

matrix/copy_transform.py

@@ -0,0 +1,62 @@
+def rotate_clockwise(matrix):
+    new = []
+    for row in reversed(matrix):
+        for i, elem in enumerate(row):
+            try:
+                new[i].append(elem)
+            except IndexError:
+                new.insert(i, [])
+                new[i].append(elem)
+    return new
+
+def rotate_counterclockwise(matrix):
+    new = []
+    for row in matrix:
+        for i, elem in enumerate(reversed(row)):
+            try:
+                new[i].append(elem)
+            except IndexError:
+                new.insert(i, [])
+                new[i].append(elem)
+    return new
+
+def top_left_invert(matrix):
+    new = []
+    for row in matrix:
+        for i, elem in enumerate(row):
+            try:
+                new[i].append(elem)
+            except IndexError:
+                new.insert(i, [])
+                new[i].append(elem)
+    return new
+
+def bottom_left_invert(matrix):
+    new = []
+    for row in reversed(matrix):
+        for i, elem in enumerate(reversed(row)):
+            try:
+                new[i].append(elem)
+            except IndexError:
+                new.insert(i, [])
+                new[i].append(elem)
+    return new
+
+if __name__ == '__main__':
+    def print_matrix(matrix, name):
+        print('{}:\n['.format(name))
+        for row in matrix:
+            print('  {}'.format(row))
+        print(']\n')
+
+    matrix = [
+        [1, 2, 3],
+        [4, 5, 6],
+        [7, 8, 9],
+    ]
+
+    print_matrix(matrix, 'initial')
+    print_matrix(rotate_clockwise(matrix), 'clockwise')
+    print_matrix(rotate_counterclockwise(matrix), 'counterclockwise')
+    print_matrix(top_left_invert(matrix), 'top left invert')
+    print_matrix(bottom_left_invert(matrix), 'bottom left invert')