Merge pull request #9 from m4tveevm/KruskalsAlgo

small refactoring and adding new solution of kruskal's algorithm

src/kruskals/disjoint_set.py

@@ -0,0 +1,23 @@
+class DisjointSet:
+    def __init__(self, n: int):
+        self.parent = [i for i in range(n)]
+        self.rank = [0] * n
+
+    def find(self, x: int) -> int:
+        if self.parent[x] != x:
+            self.parent[x] = self.find(self.parent[x])
+        return self.parent[x]
+
+    def union(self, x: int, y: int) -> bool:
+        rx = self.find(x)
+        ry = self.find(y)
+        if rx == ry:
+            return False
+        if self.rank[rx] < self.rank[ry]:
+            self.parent[rx] = ry
+        elif self.rank[rx] > self.rank[ry]:
+            self.parent[ry] = rx
+        else:
+            self.parent[ry] = rx
+            self.rank[rx] += 1
+        return True

src/kruskals/edges.py

@@ -0,0 +1,8 @@
+from dataclasses import dataclass
+
+
+@dataclass(frozen=True)
+class Edge:
+    u: int
+    v: int
+    weight: float

src/kruskals/graph.py

@@ -0,0 +1,32 @@
+from copy import copy
+from typing import List
+
+from src.kruskals.edges import Edge
+
+
+class Graph:
+    def __init__(self, vertices_count: int):
+        if vertices_count <= 0:
+            raise ValueError("Количество вершин <= 0")
+        self.vertices_count = vertices_count
+        self._edges: List[Edge] = []
+
+    @property
+    def edges(self) -> List[Edge]:
+        return copy(self._edges)
+
+    def add_edge(self, begin: int, end: int, weight: float):
+        if (
+            begin < 0
+            or end < 0
+            or begin >= self.vertices_count
+            or end >= self.vertices_count
+        ):
+            raise ValueError("Неверный индекс вершины")
+        if begin == end:
+            raise ValueError("Петли не допускаются")
+        if weight <= 0 or weight > 1023:
+            raise ValueError(
+                "Вес ребра должен быть в диапазоне [1, ..., 1023]"
+            )
+        self._edges.append(Edge(begin, end, weight))

src/kruskals/graph_reader.py

@@ -0,0 +1,56 @@
+from src.kruskals.graph import Graph
+
+
+def _process_edge(i: int, j: int, val: int, graph: Graph):
+    if val == 0:
+        return
+    if val < 1 or val > 1023:
+        raise ValueError("Вес ребра должен быть в диапазоне [1..1023].")
+    if j > i:
+        graph.add_edge(i, j, val)
+
+
+def _read_matrix_row(file_obj, vertices_count: int):
+    line = file_obj.readline().strip()
+    if not line:
+        raise ValueError("Строк в матрице меньше, чем количество вершин.")
+
+    row_values = line.split()
+    if len(row_values) != vertices_count:
+        raise ValueError(
+            "Количество столбцов матрицы не соответствует количеству вершин."
+        )
+    return row_values
+
+
+def _read_adjacency_matrix(file_obj, graph: Graph):
+    vertices_count = graph.vertices_count
+    for i in range(vertices_count):
+        row_values = _read_matrix_row(file_obj, vertices_count)
+        for j, val_str in enumerate(row_values):
+            val = int(val_str)
+            _process_edge(i, j, val, graph)
+
+
+class GraphReader:
+    def __init__(self, max_vertices=50):
+        self.max_vertices = max_vertices
+
+    def read_graph_from_file(self, filename: str):
+        with open(filename, "r", encoding="utf-8") as f:
+            vertex_names = self._read_vertex_names(f)
+            graph = Graph(len(vertex_names))
+            _read_adjacency_matrix(f, graph)
+            return graph, vertex_names
+
+    def _read_vertex_names(self, file_obj):
+        first_line = file_obj.readline().strip()
+        if not first_line:
+            raise ValueError("File is corrupt")
+
+        vertex_names = first_line.split()
+        if len(vertex_names) > self.max_vertices:
+            raise ValueError(
+                f"Слишком много вершин. Максимум {self.max_vertices}."
+            )
+        return vertex_names

src/kruskals/input.txt

@@ -0,0 +1,4 @@
+A  B  C
+0  3  1
+3  0  2
+1  2  0

src/kruskals/mst_strategy.py

@@ -0,0 +1,26 @@
+from abc import ABC, abstractmethod
+from typing import List
+
+from src.kruskals.disjoint_set import DisjointSet
+from src.kruskals.edges import Edge
+
+
+class MSTStrategy(ABC):
+    @abstractmethod
+    def find_mst(self, vertices_count: int, edges: List[Edge]) -> List[Edge]:
+        pass
+
+
+class KruskalMST(MSTStrategy):
+    def find_mst(self, vertices_count: int, edges: List[Edge]) -> List[Edge]:
+        sorted_edges = sorted(edges, key=lambda e: e.weight)
+        dsu = DisjointSet(vertices_count)
+        mst = []
+        for edge in sorted_edges:
+            if dsu.union(edge.u, edge.v):
+                mst.append(edge)
+            if len(mst) == vertices_count - 1:
+                break
+        if len(mst) != vertices_count - 1:
+            return []
+        return mst

src/kruskals/output.txt

@@ -0,0 +1,3 @@
+A C
+B C
+3

src/kruskals/solution.py

@@ -0,0 +1,38 @@
+from src.kruskals.graph_reader import GraphReader
+from src.kruskals.mst_strategy import KruskalMST
+
+
+def main():
+    input_file = "input.txt"
+    output_file = "output.txt"
+
+    reader = GraphReader()
+    graph, vertex_names = reader.read_graph_from_file(input_file)
+
+    kruskal = KruskalMST()
+    mst = kruskal.find_mst(graph.vertices_count, graph.edges)
+
+    if not mst:
+        with open(output_file, "w", encoding="utf-8") as out:
+            out.write("Остов не существует\n")
+        return
+
+    named_edges = []
+    for edge in mst:
+        v1_name = vertex_names[edge.u]
+        v2_name = vertex_names[edge.v]
+        if v1_name > v2_name:
+            v1_name, v2_name = v2_name, v1_name
+        named_edges.append((v1_name, v2_name, edge.weight))
+
+    named_edges.sort(key=lambda x: (x[0], x[1]))
+    total_weight = sum(edge[2] for edge in named_edges)
+
+    with open(output_file, "w", encoding="utf-8") as out:
+        for u_name, v_name, w in named_edges:
+            out.write(f"{u_name} {v_name}\n")
+        out.write(f"{total_weight}\n")
+
+
+if __name__ == "__main__":
+    main()

src/tree/binary_tree.py

@@ -1,4 +1,4 @@
-from .traversal import TraversalStrategy
+from src.tree.traversal import TraversalStrategy
 
 
 class BinaryTree:

test/test_disjoint_set.py

@@ -0,0 +1,33 @@
+import unittest
+
+from src.kruskals.disjoint_set import DisjointSet
+
+
+class TestDisjointSet(unittest.TestCase):
+    def test_init(self):
+        dsu = DisjointSet(5)
+        for i in range(5):
+            self.assertEqual(dsu.find(i), i)
+
+    def test_union_find(self):
+        dsu = DisjointSet(5)
+        dsu.union(0, 1)
+        self.assertEqual(dsu.find(0), dsu.find(1))
+        dsu.union(1, 2)
+        self.assertEqual(dsu.find(0), dsu.find(2))
+        self.assertNotEqual(dsu.find(3), dsu.find(0))
+
+    def test_large(self):
+        n = 50
+        dsu = DisjointSet(n)
+        for i in range(n - 1):
+            dsu.union(i, i + 1)
+        root = dsu.find(0)
+        for i in range(1, n):
+            self.assertEqual(dsu.find(i), root)
+
+    def test_no_unions(self):
+        n = 10
+        dsu = DisjointSet(n)
+        for i in range(n):
+            self.assertEqual(dsu.find(i), i)

test/test_graph.py

@@ -0,0 +1,50 @@
+import unittest
+
+from src.kruskals.graph import Graph
+
+
+class TestGraph(unittest.TestCase):
+    def test_init(self):
+        with self.assertRaises(ValueError):
+            Graph(0)
+        graph = Graph(3)
+        self.assertEqual(graph.vertices_count, 3)
+
+    def test_add_edge_valid(self):
+        graph = Graph(3)
+        graph.add_edge(0, 1, 1)
+        self.assertEqual(len(graph.edges), 1)
+
+    def test_add_edge_invalid_index(self):
+        graph = Graph(3)
+        with self.assertRaises(ValueError):
+            graph.add_edge(-1, 0, 1)
+        with self.assertRaises(ValueError):
+            graph.add_edge(0, 3, 1)
+
+    def test_add_loop_edge(self):
+        graph = Graph(3)
+        with self.assertRaises(ValueError):
+            graph.add_edge(0, 0, 1)
+
+    def test_add_negative_or_zero_weight(self):
+        graph = Graph(3)
+        with self.assertRaises(ValueError):
+            graph.add_edge(0, 1, -1)
+        with self.assertRaises(ValueError):
+            graph.add_edge(0, 1, 0)
+
+    def test_max_weight(self):
+        graph = Graph(3)
+        graph.add_edge(0, 1, 1023)
+        self.assertEqual(len(graph.edges), 1)
+        self.assertEqual(graph.edges[0].weight, 1023)
+        with self.assertRaises(ValueError):
+            graph.add_edge(1, 2, 1024)
+
+    def test_large_graph(self):
+        n = 50
+        graph = Graph(n)
+        for i in range(n - 1):
+            graph.add_edge(i, i + 1, i + 1)
+        self.assertEqual(len(graph.edges), n - 1)

test/test_graph_reader.py

@@ -0,0 +1,73 @@
+import os
+import unittest
+
+from src.kruskals.graph_reader import GraphReader
+
+
+class TestGraphReader(unittest.TestCase):
+    def setUp(self):
+        self.test_filename = "input.txt"
+
+    def tearDown(self):
+        if os.path.exists(self.test_filename):
+            os.remove(self.test_filename)
+
+    def test_empty_file(self):
+        open(self.test_filename, "w").close()
+        reader = GraphReader()
+        with self.assertRaises(ValueError):
+            reader.read_graph_from_file(self.test_filename)
+
+    def test_wrong_format(self):
+        with open(self.test_filename, "w") as file:
+            file.write("A B C\n0 1 2\n0 0")
+        reader = GraphReader()
+        with self.assertRaises(ValueError):
+            reader.read_graph_from_file(self.test_filename)
+
+    def test_too_many_vertices(self):
+        names = " ".join([f"V{i}" for i in range(51)])
+        with open(self.test_filename, "w") as file:
+            file.write(names + "\n")
+        reader = GraphReader()
+        with self.assertRaises(ValueError):
+            reader.read_graph_from_file(self.test_filename)
+
+    def test_invalid_weight(self):
+        with open(self.test_filename, "w") as file:
+            file.write("A B\n0 1024\n1024 0\n")
+        reader = GraphReader()
+        with self.assertRaises(ValueError):
+            reader.read_graph_from_file(self.test_filename)
+
+    def test_valid_graph(self):
+        with open(self.test_filename, "w") as file:
+            file.write("A B C\n0 3 1\n3 0 2\n1 2 0\n")
+        reader = GraphReader()
+        graph, names = reader.read_graph_from_file(self.test_filename)
+        self.assertEqual(len(names), 3)
+        self.assertEqual(graph.vertices_count, 3)
+        self.assertEqual(len(graph.edges), 3)
+        weights = sorted(edge.weight for edge in graph.edges)
+        self.assertEqual(weights, [1, 2, 3])
+
+    def test_full_graph(self):
+        """
+        Полный граф из 4 вершин
+        Вершины: A B C D
+        Матрица:
+        0 1 2 3
+        1 0 4 5
+        2 4 0 6
+        """
+
+        with open(self.test_filename, "w") as file:
+            file.write("A B C D\n")
+            file.write("0 1 2 3\n")
+            file.write("1 0 4 5\n")
+            file.write("2 4 0 6\n")
+            file.write("3 5 6 0\n")
+        reader = GraphReader()
+        g, names = reader.read_graph_from_file(self.test_filename)
+        self.assertEqual(len(g.edges), 6)
+        self.assertEqual(sorted(names), ["A", "B", "C", "D"])