add solutions week 281 in python

2 files changed, 77 insertions, 0 deletions

diff --git a/challenge-281/steven-wilson/python/ch-1.py b/challenge-281/steven-wilson/python/ch-1.py
new file mode 100644
index 0000000000..a497fced01
--- /dev/null
+++ b/challenge-281/steven-wilson/python/ch-1.py
@@ -0,0 +1,21 @@
+#!/usr/bin/env python3
+
+
+def check_colour(coordinates):
+    """ Given coordinates, a string that represents the coordinates of a square
+    of the chessboard return true if the square is light, and false if the
+    square is dark
+    >>> check_colour("d3")
+    True
+    >>> check_colour("g5")
+    False
+    >>> check_colour("e6")
+    True
+    """
+    return not (ord(coordinates[0]) + int(coordinates[1])) % 2 == 0
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod(verbose=True)
diff --git a/challenge-281/steven-wilson/python/ch-2.py b/challenge-281/steven-wilson/python/ch-2.py
new file mode 100644
index 0000000000..2060cce74d
--- /dev/null
+++ b/challenge-281/steven-wilson/python/ch-2.py
@@ -0,0 +1,56 @@
+#!/usr/bin/env python3
+
+from collections import deque
+
+
+def knights_move(start, end):
+    """ A Knight in chess can move from its current position to any square two
+    rows or columns plus one column or row away.  Take a starting position and
+    an ending position and calculate the least number of moves required.
+
+    >>> knights_move('g2', 'a8') # g2 -> e3 -> d5 -> c7 -> a8
+    4
+    >>> knights_move('g2', 'h2') # g2 -> e3 -> f1 -> h2
+    3
+    """
+    start_p = (ord(start[0]) - 96, int(start[1]))
+    end_p = (ord(end[0]) - 96, int(end[1]))
+    queue = deque([start_p])
+    visited = {start_p}
+    number_moves = 0
+    while queue:
+        for _ in range(len(queue)):
+            current = queue.popleft()
+
+            if current == end_p:
+                return number_moves
+
+            for position in possible_moves(current):
+                if position not in visited:
+                    visited.add(position)
+                    queue.append(position)
+        number_moves += 1
+    return -1
+
+
+def possible_moves(position):
+    '''
+    Return all possible knight moves within the board from a position
+
+    >>> possible_moves((4, 4))
+    [(6, 5), (5, 6), (3, 6), (2, 5), (2, 3), (3, 2), (5, 2), (6, 3)]
+    >>> possible_moves((1, 1))
+    [(3, 2), (2, 3)]
+    '''
+    moves = ([2, 1], [1, 2], [-1, 2], [-2, 1], [-2, -1], [-1, -2], [1, -2],
+             [2, -1])
+    return [(position[0] + move[0], position[1] + move[1])
+            for move in moves
+            if (position[0] + move[0]) in range(1, 9)
+            and (position[1] + move[1]) in range(1, 9)]
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod(verbose=True)