Python 图算法

inf = float("inf")  # inf的值大于任何float类型的值


class GraphError(ValueError):
    pass

邻接矩阵实现

class Graph:
    def __init__(self, mat, unconn=0):
        vnum = len(mat)
        for x in mat:
            if len(x) != vnum:      # 检查是否为方阵
                raise ValueError("Argument for 'Graph' . ")
        self._mat = [mat[i][:] for i in range(vnum)]    # 做拷贝
        self._unconn = unconn
        self._vnum = vnum

    def vertex_num(self):
        return self._vnum

    def _invalid(self, v):
        return 0 > v or v >= self._vnum

    def add_vertex(self):
        raise GraphError( \
            "Adj-Matrix dose not support 'add_vertex' . ")

    def add_edge(self, vi, vj, val=1):
        if self._invalid(vi) or self._invalid(vj):
            raise GraphError(str(vi) + 'or' + str(vj) + /
                            " is not a valid verdex. ")
        self._mat[vi][vj] = val

    def get_edge(self, vi, vj):
        if self._invalid(vi) or self._invalid(vj):
            raise GraphError(str(vi) + 'or' + str(vj) + /
                            " is not a valid verdex. ")
        return self._mat[vi][vj]

    def out_edges(self, vi):    # 获得从v出发的所有边
        raise GraphError( \
            "Adj-Matrix dose not support 'add_vertex' . ")
        return self._out_edges(self._mat[vi], self._unconn)

    @staticmethod
    def _out_edges(row, unconn):
        edges = []
        for i in range(len(row)):
            if row[i] != unconn:
                edges.append((i, row[i]))