python中有向图的单调着色

from collections import defaultdict

class Graph:
    def __init__(self, vertices):
        self.V = vertices
        self.graph = defaultdict(list)

    def add_edge(self, u, v):
        self.graph[u].append(v)

    def topological_sort_util(self, v, visited, stack):
        visited[v] = True
        for i in self.graph[v]:
            if not visited[i]:
                self.topological_sort_util(i, visited, stack)
        stack.insert(0, v)

    def topological_sort(self):
        visited = [False] * self.V
        stack = []
        for i in range(self.V):
            if not visited[i]:
                self.topological_sort_util(i, visited, stack)
        return stack

    def monotone_coloring(self):
        topo_order = self.topological_sort()
        colors = [-1] * self.V
        color = 0
        for vertex in topo_order:
            visited = [False] * self.V
            for neighbor in self.graph[vertex]:
                if colors[neighbor] != -1:
                    visited[colors[neighbor]] = True
            while visited[color]:
                color += 1
            colors[vertex] = color
        return colors

# 示例用法
g = Graph(6)
g.add_edge(5, 2)
g.add_edge(5, 0)
g.add_edge(4, 0)
g.add_edge(4, 1)
g.add_edge(2, 3)
g.add_edge(3, 1)

print("单调着色结果:", g.monotone_coloring())