错误的递归函数来寻找可能的路线的数量

Question

我使用嵌套的字典来指示图的顶点和边，如：

[ 
A: [B,D,E], 
B: [C], 
C: [D,E], 
D: [C,E], 
E: [B] 
] 

这是我到目前为止的代码：

def number_of_trips(self, start_point, end_point, maxstops): 
    return self._find_path(start_point, end_point, 0, 0, maxstops) 

def _find_path(self, point_a, end_point, current_stops, routes, maxstops): 
    current_stops += 1 

    if current_stops > maxstops: 
     return routes 

    if end_point in self.digraph[point_a]: 
     return routes + 1 
    else: 
     for x in self.digraph[point_a]: 
      return self._find_path(x, end_point, current_stops, routes, maxstops) 

    return routes 

并且该方法被称为像这样：

number_of_trips('C', 'C', 3) 

，其输出1，而不是2

我的递归函数有什么问题？

Answer 1

问题用下面的代码解决：

def _find_path(self, point_a, end_point, current_stops, routes, maxstops): 
     current_stops += 1 

     if current_stops > maxstops: 
      return routes 

     if end_point in self.digraph[point_a]: 
      return 1 
     else: 
      for x in self.digraph[point_a]: 
       routes += self._find_path(x, end_point, current_stops, routes, maxstops) 

     return routes 

Answer 2

增量当递归调用作出routes值：

return self._find_path(x, end_point, current_stops, routes + 1, maxstops)