Tasks from november 20

.github/workflows/main.yml

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+name: Ruff
+on: push
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.13.7"
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install ruff pytest
+      - name: Run Ruff
+        run: ruff check --output-format=github .
+      - name: Run unit-tests
+        run: python -m pytest tests/*

src/dfs.py

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+class Graph:
+    def init(self):
+        self.adj = {}
+        self._dfs_order = None  # порядок обхода для итерации
+
+    def add_vertex(self, v):
+        if v not in self.adj:
+            self.adj[v] = []
+
+    def add_edge(self, u, v):
+        self.add_vertex(u)
+        self.add_vertex(v)
+        self.adj[u].append(v)
+        self.adj[v].append(u)
+
+    def dfs(self, start):
+        visited = set()
+        order = []
+
+        def _dfs(v):
+            visited.add(v)
+            order.append(v)
+            for nxt in self.adj[v]:
+                if nxt not in visited:
+                    _dfs(nxt)
+
+        _dfs(start)
+        self._dfs_order = order  # граф станет итерируемым в этом порядке
+        return order
+
+    def iter(self):
+        # итерируем граф в порядке последнего DFS
+        if self._dfs_order is None:
+            raise RuntimeError(
+                "Сначала нужно вызвать dfs(), чтобы определить порядок итерации"
+            )
+        return iter(self._dfs_order)

tests/test_dfs.py

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+from src.dfs import Graph
+
+
+def test_dfs_order():
+    g = Graph()
+    g.add_edge(1, 2)
+    g.add_edge(1, 3)
+    g.add_edge(2, 4)
+    g.add_edge(2, 5)
+
+    result = g.dfs(1)
+    assert result == [1, 2, 4, 5, 3]
+
+
+def test_iteration_after_dfs():
+    g = Graph()
+    g.add_edge("A", "B")
+    g.add_edge("A", "C")
+    g.add_edge("B", "D")
+
+    order = g.dfs("A")
+    assert list(g) == order