算法导论--BFS、DFS及拓扑排序

算法导论--BFS，DFS及拓扑排序

class Graph(object):
    _max_weight=10000
    _White,_Gray,_Black=0,1,2
    time = 0
    def __init__(self):
        self._num=0
        self._g=[]
        self._prev=[]
        self._w=[]
        self._rg=[]
        self._visit=[]
        self._f=[]
        self._topological=[]

    def _clear(self):
        self.__class__.time=0
       for i in range(self._num):
            self._visit[i]=self.__class__._White
            self._prev[i]=-1
            self._w[i]=self.__class__._max_weight
            self._f[i]=0
    def Input(self):
        self._num=input('输入顶点数：')
        self.__class__.time=0
        for i in range(self._num):
            self._rg.append([])
            self._visit.append(self.__class__._White)
            self._prev.append(-1)
            self._w.append(self.__class__._max_weight)
            self._f.append(0)
        for i in range(self._num):
            v=map(int,raw_input().split())
            for j in v:
                self._rg[j].append(i)
            self._g.append(v)
    def BFS(self,s):
        self._clear()
        self._visit[s]=self.__class__._Gray
        self._w[s]=0
        queue=[]
        queue.append(s)
        while queue:
            u=queue.pop()
            for i in self._g[u]:
                if self._visit[i]==self.__class__._White:
                    self._visit[i]=self.__class__._Gray
                    self._prev[i]=u
                    self._w[i]=self._w[u]+1
                    queue.append(i)
            self._visit[u]=self.__class__._Black
    def BFSPath(self,s,v):
        if v==s:
            print s,'->',
        elif self._prev[v]==-1:
            print 'no path from ',s,' to ',v
        else:
            self.BFSPath(s,self._prev[v])
            print v,'->',
    def DFS(self):
        self._clear()
        for v in range(self._num):
            if self._visit[v] == self.__class__._White:
                self._dfs_visit(v)
    def _dfs_visit(self,u):
        self._visit[u]=self.__class__._Gray
        self.__class__.time+=1
        self._w[u]=self.__class__.time
        for v in self._g[u]:
            if self._visit[v] == self.__class__._White:
                self._prev[v]=u
                self._dfs_visit(v)
        self._visit[u]=self.__class__._Black
        self.__class__.time+=1
        self._f[u]=self.__class__.time
        self._topological.insert(0,u)
        
    Topological=DFS
    
    def __str__(self):
        return '\n'.join(' '.join(map(str,sublist)) for sublist in self._g)


if __name__=='__main__':
    g=Graph()
    g.Input()
    g.BFS(0)
    g.BFSPath(0,2)
    #g.DFS()
    g.Topological()