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python_prototype/backtrack.py

@@ -60,13 +60,34 @@ def get_constraints(board: list, border: list, pos: int) -> list:
     constraints = [colup, coldown, rowleft, rowright]
     return constraints
 
+def check_constraint(slice: list, constraint: int) -> bool:
+    print(f'{slice=}')
+    print(f'0 in slice: {0 in slice}')
+    if 0 in slice:
+        return True
+    level = 0
+    visible_towers = 0
+    for tower in slice:
+        if tower > level:
+            level = tower
+            visible_towers += 1
+    print(f'{visible_towers=} vs {constraint=}')
+    return visible_towers == int(constraint)
+
 def is_valid_state(board: list, border: list, next_candidate_index: int) -> bool:
     print_board(board, border)
     row = get_row(board, next_candidate_index)
     column = get_col(board, next_candidate_index)
     constraints = get_constraints(board, border, next_candidate_index)
     print(f'{constraints=}, {row=}, {column=}')
-    return True
+    satisfies_constraints = all([
+        check_constraint(row,          constraints[2]),
+        check_constraint(row[::-1],    constraints[3]),
+        check_constraint(column,       constraints[0]),
+        check_constraint(column[::-1], constraints[1])
+    ])
+    print(f'{satisfies_constraints=}')
+    return satisfies_constraints
 
 def print_board(board: list, border: list) -> None:
     padding = ' ' * PADDING
@@ -84,6 +105,8 @@ def print_board(board: list, border: list) -> None:
     print(' '.join(border[board_dim:board_dim * 2]))
     print()
 
+# 2D board initialized with 0's, dependent on n
+# params: rec-depth, n, **board, **border
 def backtrack(board: list, sols: list, border: list) -> None:
     if board.count(0) == 0:
         sols.append(board)