reorganise directories

upd chapter_01/binary.py

chapter_06/README.md

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+# Breadth-First Search
+
+Can tell you if there's a path between A and B and will find the shortest.
+
+In these examples, 1st degree Mango sellers are found before 2nd degree, 2nd before 3rd and so on.
+
+Visted nodes should be stored in a set to ensure no infinite loops.
+
+Running time for BFS on a directed graph: `O(V + E`) where V = vertices, E = edges.

chapter_06/ex6.1.py

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+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": [],
+}
+
+visited = set()
+
+
+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
+
+        if current_node.name in visited:
+            continue
+        visited.add(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 s to f: {distance}")

chapter_06/ex6.2.py

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+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 = set()
+
+
+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.add(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}")

chapter_06/mango.py

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+import logging
+from collections import deque
+from dataclasses import dataclass
+
+logging.basicConfig(level=logging.DEBUG)
+logger = logging.getLogger(__name__)
+
+
+@dataclass
+class Person:
+    name: str
+    distance: int
+
+    @property
+    def is_seller(self):
+        return self.name.endswith("m")
+
+
+graph = {
+    "you": [
+        Person("bob", 1),
+        Person("claire", 1),
+        Person("alice", 1),
+    ],
+    "claire": [
+        Person("thom", 0),
+        Person("jonny", 0),
+    ],
+    "alice": [
+        Person("peggy", 0),
+    ],
+    "bob": [
+        Person("peggy", 0),
+        Person("anuj", 0),
+    ],
+    "thom": [],
+    "jonny": [],
+    "peggy": [],
+    "anuj": [],
+}
+
+visited = set()
+
+
+def bfs():
+    queue = deque()
+    queue += graph["you"]
+
+    while queue:
+        logger.debug(queue)
+        current_person = queue.popleft()
+        if current_person.is_seller:
+            return current_person
+
+        if current_person.name in visited:
+            continue
+        visited.add(current_person.name)
+
+        next_persons = graph[current_person.name]
+        for p in next_persons:
+            p.distance = current_person.distance + 1
+        queue += next_persons
+
+
+to_word = ["", "first", "second", "third"]
+
+person = bfs()
+print(f"{person.name} is a {to_word[person.distance]} degree mango seller.")