python version functional

solver.py

@@ -0,0 +1,151 @@
+from grid import *
+from copy import deepcopy
+
+def solve(G):
+    stack = [G]
+    while len(stack) > 0:
+        grid = stack.pop()
+        ret = simplify(grid)
+        if ret == 0:
+            branch(grid, stack)
+    print(G)
+    printn("unsolvable!")
+
+def simplify(G):
+    sum = 1
+    while sum > 0:
+        sum = 0
+        ret = check_rows(G)
+        if ret < 0:
+            return -1
+        else:
+            sum += ret
+    
+        ret = check_cols(G)
+        if ret < 0:
+            return -1
+        else:
+            sum += ret
+    
+        ret = check_squares(G)
+        if ret < 0:
+            return -1
+        else:
+            sum += ret
+    
+        ret = reduce(G)
+        if ret < 0:
+            return -1
+        else:
+            sum += ret
+    return 0
+
+def branch(G, stack):
+    min_cell = None
+    min_cell_size = 10
+    for cell in G.cells:
+        if cell.is_set == False and len(cell.candidates) < min_cell_size:
+            min_cell = cell
+            min_cell_size = len(cell.candidates)
+    candidates = min_cell.candidates
+    for candidate in candidates:
+        copy = deepcopy(G)
+        copy.cells[min_cell.n].set(candidate)
+        stack.append(copy)
+
+def reduce(G):
+    n_steps = 0
+    while True:
+        val = reduce_step(G)
+        if val == 0:
+            print(G)
+            print("done")
+            exit(0)
+        elif val == 1:
+            return n_steps
+        n_steps += 1
+
+def reduce_step(G):
+    all_set = True
+    nochange = True
+    for cell in G.cells:
+        l = len(cell.candidates)
+        if not cell.is_set:
+            if l == 1:
+                cell.set(cell.candidates[0])
+                nochange = False
+            else:
+                all_set = False
+    if all_set:
+        return 0
+    elif nochange:
+        return 1
+    else:
+        return 2
+
+def check_rows(G):
+    res = 0
+    for row in G.rows:
+        finds = [0]*9
+        to_set = []
+        for cell in row:
+            cell = G.cells[cell]
+            for candidate in cell.candidates:
+                finds[candidate-1] += 1
+        for i, find in enumerate(finds):
+            if find == 1:
+                to_set.append(i+1)
+            elif find == 0:
+                return -1
+        for cell in row:
+            cell = G.cells[cell]
+            for i in to_set:
+                if i in cell.candidates and not cell.is_set:
+                    cell.set(i)
+                    res += 1
+    return res
+
+def check_cols(G):
+    res = 0
+    for col in G.cols:
+        finds = [0]*9
+        to_set = []
+        for cell in col:
+            cell = G.cells[cell]
+            for candidate in cell.candidates:
+                finds[candidate-1] += 1
+        for i, find in enumerate(finds):
+            if find == 1:
+                to_set.append(i+1)
+            elif find == 0:
+                return -1
+        for cell in col:
+            cell = G.cells[cell]
+            for i in to_set:
+                if i in cell.candidates and not cell.is_set:
+                    cell.set(i)
+                    res += 1
+    return res
+
+def check_squares(G):
+    res = 0
+    for square in G.squares:
+        finds = [0]*9
+        to_set = []
+        for cell in square:
+            cell = G.cells[cell]
+            for candidate in cell.candidates:
+                finds[candidate-1] += 1
+        for i, find in enumerate(finds):
+            if find == 1:
+                to_set.append(i+1)
+            elif find == 0:
+                return -1
+        for cell in square:
+            cell = G.cells[cell]
+            for i in to_set:
+                if i in cell.candidates and not cell.is_set:
+                    cell.set(i)
+                    res += 1
+    return res
+