hello-algo/codes/python/chapter_graph/graph_adjacency_list.py

"""
File: graph_adjacency_list.py
Created Time: 2023-02-23
Author: Krahets (krahets@163.com)
"""

import sys
from pathlib import Path

sys.path.append(str(Path(__file__).parent.parent))
from modules import Vertex, vals_to_vets


class GraphAdjList:
    """基于邻接表实现的无向图类"""

    def __init__(self, edges: list[list[Vertex]]):
        """构造方法"""
        # 邻接表，key: 顶点，value：该顶点的所有邻接顶点
        self.adj_list = dict[Vertex, list[Vertex]]()
        # 添加所有顶点和边
        for edge in edges:
            self.add_vertex(edge[0])
            self.add_vertex(edge[1])
            self.add_edge(edge[0], edge[1])

    def size(self) -> int:
        """获取顶点数量"""
        return len(self.adj_list)

    def add_edge(self, vet1: Vertex, vet2: Vertex):
        """添加边"""
        if vet1 not in self.adj_list or vet2 not in self.adj_list or vet1 == vet2:
            raise ValueError()
        # 添加边 vet1 - vet2
        self.adj_list[vet1].append(vet2)
        self.adj_list[vet2].append(vet1)

    def remove_edge(self, vet1: Vertex, vet2: Vertex):
        """删除边"""
        if vet1 not in self.adj_list or vet2 not in self.adj_list or vet1 == vet2:
            raise ValueError()
        # 删除边 vet1 - vet2
        self.adj_list[vet1].remove(vet2)
        self.adj_list[vet2].remove(vet1)

    def add_vertex(self, vet: Vertex):
        """添加顶点"""
        if vet in self.adj_list:
            return
        # 在邻接表中添加一个新链表
        self.adj_list[vet] = []

    def remove_vertex(self, vet: Vertex):
        """删除顶点"""
        if vet not in self.adj_list:
            raise ValueError()
        # 在邻接表中删除顶点 vet 对应的链表
        self.adj_list.pop(vet)
        # 遍历其他顶点的链表，删除所有包含 vet 的边
        for vertex in self.adj_list:
            if vet in self.adj_list[vertex]:
                self.adj_list[vertex].remove(vet)

    def print(self):
        """打印邻接表"""
        print("邻接表 =")
        for vertex in self.adj_list:
            tmp = [v.val for v in self.adj_list[vertex]]
            print(f"{vertex.val}: {tmp},")


"""Driver Code"""
if __name__ == "__main__":
    # 初始化无向图
    v = vals_to_vets([1, 3, 2, 5, 4])
    edges = [
        [v[0], v[1]],
        [v[0], v[3]],
        [v[1], v[2]],
        [v[2], v[3]],
        [v[2], v[4]],
        [v[3], v[4]],
    ]
    graph = GraphAdjList(edges)
    print("\n初始化后，图为")
    graph.print()

    # 添加边
    # 顶点 1, 2 即 v[0], v[2]
    graph.add_edge(v[0], v[2])
    print("\n添加边 1-2 后，图为")
    graph.print()

    # 删除边
    # 顶点 1, 3 即 v[0], v[1]
    graph.remove_edge(v[0], v[1])
    print("\n删除边 1-3 后，图为")
    graph.print()

    # 添加顶点
    v5 = Vertex(6)
    graph.add_vertex(v5)
    print("\n添加顶点 6 后，图为")
    graph.print()

    # 删除顶点
    # 顶点 3 即 v[1]
    graph.remove_vertex(v[1])
    print("\n删除顶点 3 后，图为")
    graph.print()