complete puzzle

session-1-puzzled/puzzle-complete.py

+from microbit import *
+
+size = 3
+
+grid = [[4, 1, 3],
+        [7, 2, 6],
+        [0, 5, 8]]
+
+solvedGrid = [[1, 2, 3],
+              [4, 5, 6],
+              [7, 8, 0]]
+
+
+def copy(grid):
+    return [[y for y in x] for x in grid]
+
+
+def isSolved(grid):
+    return grid == solvedGrid
+
+
+def showGrid(grid):
+    for x in range(1, size + 1):
+        for y in range(1, size + 1):
+            display.set_pixel(y, x, grid[x-1][y-1])
+
+
+def lightUp():
+    display.set_pixel(0, 0, 9)
+    display.set_pixel(0, 4, 9)
+    display.set_pixel(4, 0, 9)
+    display.set_pixel(4, 4, 9)
+
+
+def getMoves(grid):
+    # find the zero
+    for x in range(size):
+        for y in range(size):
+            if grid[x][y] == 0:
+                zerox = x
+                zeroy = y
+
+    # where can we move?
+    xswaps = [((zerox, zeroy), (x, zeroy)) for x in [zerox - 1, zerox + 1]
+              if x >= 0 and x < size]
+    yswaps = [((zerox, zeroy), (zerox, y)) for y in [zeroy - 1, zeroy + 1]
+              if y >= 0 and y < size]
+
+    return xswaps + yswaps
+
+
+def swap(grid, move):
+    pos0, pos1 = move
+    x0, y0 = pos0
+    x1, y1 = pos1
+    tmp = grid[x0][y0]
+    grid[x0][y0] = grid[x1][y1]
+    grid[x1][y1] = tmp
+
+
+# distance of current grid to target grid, defined as number of pieces that are
+# in the wrong position
+def distance(grid, move):
+    swap(grid, move)
+    diff = 0
+    for x in range(size):
+        for y in range(size):
+            diff += solvedGrid[x][y] != grid[x][y]
+    swap(grid, (move[1], move[0]))
+    return diff
+
+
+visited = []
+toVisit = [grid]
+
+
+def bfs():
+    while len(toVisit) > 0:
+        grid = toVisit.pop()
+        visited.append(copy(grid))
+        showGrid(grid)
+        sleep(500)
+
+        if isSolved(grid):
+            return grid
+
+        moves = getMoves(grid)
+        # sort according to score
+        moves.sort(key = lambda e: distance(grid, e), reverse = True)
+
+        for move in moves:
+            swap(grid, move)
+            if grid not in visited:
+                toVisit.append(copy(grid))
+            swap(grid, (move[1], move[0]))
+
+
+showGrid(grid)
+grid = bfs()
+lightUp()