我认为将v的水平设为v的最长有向路径的长度可能对您来说很好。在Python中：
# the level of v is the length of the longest directed path from vdef assignlevel(graph, v, level): if v not in level: if v not in graph or not graph[v]: level[v] = 0 else: level[v] = max(assignlevel(graph, w, level) + 1 for w in graph[v]) return level[v]g = {'a': ['b', 'c'], 'b': ['d'], 'd': ['e'], 'c': ['e']}l = {}for v in g: assignlevel(g, v, l)print l输出：
{'a': 3, 'c': 1, 'b': 2, 'e': 0, 'd': 1}
