add bfs

chapter6/ex6.1.py

@@ -0,0 +1,42 @@
+import logging
+from collections import deque
+from dataclasses import dataclass
+
+logging.basicConfig(level=logging.DEBUG)
+logger = logging.getLogger(__name__)
+
+
+@dataclass
+class Node:
+    name: str
+    distance: int
+
+
+graph = {
+    "s": [Node("a", 1), Node("b", 1)],
+    "a": [Node("c", 0), Node("f", 0)],
+    "b": [Node("c", 0), Node("d", 0)],
+    "c": [],
+    "d": [Node("f", 0)],
+    "f": [],
+}
+
+
+def bfs():
+    queue = deque()
+    queue += graph["s"]
+
+    while queue:
+        logger.debug(queue)
+        current_node = queue.popleft()
+        if current_node.name == "f":
+            return current_node.distance
+
+        next_nodes = graph[current_node.name]
+        for node in next_nodes:
+            node.distance = current_node.distance + 1
+        queue += next_nodes
+
+
+distance = bfs()
+print(f"shortest distance from s to f: {distance}")

chapter6/ex6.2.py

@@ -0,0 +1,48 @@
+import logging
+from collections import deque
+from dataclasses import dataclass
+
+logging.basicConfig(level=logging.DEBUG)
+logger = logging.getLogger(__name__)
+
+
+@dataclass
+class Node:
+    name: str
+    distance: int
+
+
+graph = {
+    "cab": [Node("cat", 1), Node("car", 1)],
+    "cat": [Node("mat", 0), Node("bat", 0)],
+    "car": [Node("cat", 0), Node("bar", 0)],
+    "mat": [Node("bat", 0)],
+    "bar": [Node("bat", 0)],
+    "bat": [],
+}
+
+visited = []
+
+
+def bfs():
+    queue = deque()
+    queue += graph["cab"]
+
+    while queue:
+        logger.debug(queue)
+        current_node = queue.popleft()
+        if current_node.name == "bat":
+            return current_node.distance
+
+        if current_node.name in visited:
+            continue
+        visited.append(current_node.name)
+
+        next_nodes = graph[current_node.name]
+        for node in next_nodes:
+            node.distance = current_node.distance + 1
+        queue += next_nodes
+
+
+distance = bfs()
+print(f"shortest distance from cab to bat: {distance}")