将 python 函数转换为 r 函数

问：

我在 python 中定义了一个带有输入的函数

nodes=['A7', 'A9', 'A6', 'A1', 'A3', 'A4', 'A5', 'A8', 'A2']
graph={'A7': ['A8', 'A9', 'A6', 'A5'],
 'A9': ['A8', 'A5', 'A4', 'A7'],
 'A6': ['A7', 'A3', 'A5', 'A8', 'A2'],
 'A1': ['A3', 'A4', 'A2'],
 'A3': ['A6', 'A1', 'A4', 'A5'],
 'A4': ['A9', 'A3', 'A1', 'A5'],
 'A5': ['A7', 'A9', 'A6', 'A3', 'A4'],
 'A8': ['A7', 'A9', 'A6', 'A2'],
 'A2': ['A8', 'A6', 'A1']}
start = 'A9'
end = ['A1']
max_depth=5
def get_all_best_routes(graph,start,end,max_depth):
    past_path = []
    # maintain a queue of paths
    queue = []
    # push the first path into the queue
    queue.append([start])
    while queue:
        # get the first path from the queue
        path = queue.pop(0)
        # get the last node from the path
        node = path[-1]
        # path found
       # print "*"
        # enumerate all adjacent nodes, construct a new path and push it into the queue
        for adjacent in graph.get(node, []):
            new_path = list(path)
            ## end the current loop if we already reach the point
            if adjacent in end:
                new_path.append(adjacent)
                past_path.append(new_path)
                continue
            
            if adjacent in new_path:
                continue

            new_path.append(adjacent)
            if len(new_path) >= max_depth and new_path[-1] not in end:
                break
           # print new_path
            queue.append(new_path)
            past_path.append(new_path)
    
    best_paths = []
    for l in past_path:
        if l[-1] in end:
            best_paths.append(l)
    return best_paths

代码的步骤已经在 python 代码的取消注释行中进行了描述。 我正在尝试用 r 代码编写这个 python 函数，输入如下

# Define the nodes and graph
node <- list("A9", "A8", "A4", "A5", "A7", "A2", "A6", "A1", "A3")

graph <- list()
graph[["A9"]] <- list("A8", "A4", "A5", "A7")
graph[["A8"]] <- list("A2", "A6", "A7", "A9")
graph[["A4"]] <- list("A5", "A9", "A1", "A3")
graph[["A5"]] <- list("A3", "A6", "A7", "A9", "A4")
graph[["A7"]] <- list("A6", "A8", "A9", "A5")
graph[["A2"]] <- list("A8", "A1", "A6")
graph[["A6"]] <- list("A2", "A8", "A3", "A5", "A7")
graph[["A1"]] <- list("A2", "A3", "A4")
graph[["A3"]] <- list("A4", "A6", "A1", "A5")

max_depth <- 5
start <- "A9"
end <- c("A1")

我试过了

get_all_best_routes <- function(graph, start, end, max_depth) {
  past_path <- list()
  queue <- list()
  queue[[1]] <- list(start)
  while (length(queue) > 0) {
    path <- queue[[1]]
    queue <- queue[-1]
    node  <-  tail(path, 1)
    for (adjacent in  graph[names(graph) %in% node]) {
      new_path <- list(path)
      if (adjacent %in% end) {
        new_path <- c(new_path, adjacent)
        past_path <- c(past_path, list(new_path))
        next
      }

      if (adjacent %in% new_path) {
        next
      }

      new_path <- c(new_path, adjacent)

      if (length(new_path) >= max_depth && !(new_path[length(new_path)] %in% end)) {
        break
      }

      queue <- c(queue, new_path)
      past_path <- c(past_path, new_path)
    }
  }

  best_paths <- list()

  for (l in past_path) {
    if (l[length(l)] %in% end) {
      best_paths <- c(best_paths, l)
    }
  }

  return(best_paths)
}

有了这个，我发现了类似
Error in if (adjacent %in% end) { : the condition has length \> 1

我需要您的帮助进行此调试，非常感谢您的帮助。