add chapter 18 and 19 for 4th edition

agents_4e.py

@@ -514,7 +514,7 @@ def add_thing(self, thing, location=(1, 1), exclude_duplicate_class_items=False)
     def is_inbounds(self, location):
         """Checks to make sure that the location is inbounds (within walls if we have walls)"""
         x, y = location
-        return not (x < self.x_start or x >= self.x_end or y < self.y_start or y >= self.y_end)
+        return not (x < self.x_start or x > self.x_end or y < self.y_start or y > self.y_end)
 
     def random_location_inbounds(self, exclude=None):
         """Returns a random location that is inbounds (within walls if we have walls)"""

games4e.py

@@ -210,12 +210,12 @@ def backprop(n, utility):
 
     root = MCT_Node(state=state)
 
-    while N > 0:
+    for _ in range(N):
         leaf = select(root)
         child = expand(leaf)
         result = simulate(game, child.state)
         backprop(child, result)
-        N -= 1
+
     max_state = max(root.children, key=lambda p: p.N)
 
     return root.children.get(max_state)