R语言函数可打印网格路径但无法存储，求解决方法

你的代码核心问题在于作用域处理错误：在pathmaker函数中对paths的赋值没有修改全局变量，仅在函数局部创建了同名变量，导致最终storepaths拿到的是空的局部变量；同时路径索引使用字符串类型，不符合你按数字序号调用的需求。

修改方案1：修正全局变量作用域（简单直接） #

通过<<-运算符修改全局paths，并改用数字索引实现序号调用：

numbmatrix <- rbind(c(rep(0,times=8)),cbind(c(rep(0,times=8)),matrix(1:48,nrow=8,ncol=6),c(rep(0,times=8))),c(rep(0,times=8)))
possmoves <- cbind(rbind(1,-1),rbind(1,0),rbind(1,1),rbind(0,1),rbind(-1,1),rbind(-1,0),rbind(-1,-1),rbind(0,-1))

oneawayfrom <- function(startrow,startcol){
  visited <- matrix(0,nrow=10,ncol=8)
  oneaway <- list()
  for (i in 1:8){
    dx <- possmoves[1,i]
    dy <- possmoves[2,i]
    nextmove <- numbmatrix[startrow + dy,startcol + dx]
    if (nextmove == 0 | visited[startrow + dy,startcol + dx] != 0 ){next}
    if (visited[startrow + dy,startcol + dx] == 0 && nextmove !=0){
      visited[startrow + dy,startcol + dx] <- 1
      oneaway[[length(oneaway)+1]]<- nextmove
    }
  }
  return(oneaway)
}
options <- list()
for (i in 2:9){
  for (n in 2:7){
    adjacent <- oneawayfrom(i,n)
    cell_key <- as.character(numbmatrix[i,n])
    options[[cell_key]] <- adjacent
  }
}
paths <- list()
path_counter <- 1
pathmaker <- function(current_path){
  if (length(current_path) == 48) {
    # 使用<<-修改全局paths，直接用数字作为索引
    paths[[path_counter]] <<- current_path
    print(paste(current_path, collapse=",")) # 打印格式更清晰
    path_counter <<- path_counter + 1
    return() # 路径完成后无需返回值
  }
  last_element <- current_path[length(current_path)]
  for(i in seq_along(options[[as.character(last_element)]])){
    adjacent_number <- options[[as.character(last_element)]][i]
    if (!(adjacent_number %in% current_path)){
      pathmaker(c(current_path, adjacent_number))
    }
  }
}
# 生成路径
pathmaker(current_path=c(numbmatrix[2,2]))
# 赋值给storepaths用于后续调用
storepaths <- paths

修改说明： #

1. 用paths[[path_counter]] <<- current_path修改全局paths，确保所有递归分支共享同一个路径列表
2. 直接使用数字path_counter作为列表索引，实现storepaths[[1]]、storepaths[[2]]这类序号调用
3. 路径完成时直接return()，无需返回paths，全局变量已同步更新

修改方案2：无全局变量的函数式写法（更规范） #

避免全局变量副作用，通过递归返回值传递路径数据：

numbmatrix <- rbind(c(rep(0,times=8)),cbind(c(rep(0,times=8)),matrix(1:48,nrow=8,ncol=6),c(rep(0,times=8))),c(rep(0,times=8)))
possmoves <- cbind(rbind(1,-1),rbind(1,0),rbind(1,1),rbind(0,1),rbind(-1,1),rbind(-1,0),rbind(-1,-1),rbind(0,-1))

oneawayfrom <- function(startrow,startcol){
  visited <- matrix(0,nrow=10,ncol=8)
  oneaway <- list()
  for (i in 1:8){
    dx <- possmoves[1,i]
    dy <- possmoves[2,i]
    nextmove <- numbmatrix[startrow + dy,startcol + dx]
    if (nextmove == 0 | visited[startrow + dy,startcol + dx] != 0 ){next}
    if (visited[startrow + dy,startcol + dx] == 0 && nextmove !=0){
      visited[startrow + dy,startcol + dx] <- 1
      oneaway[[length(oneaway)+1]]<- nextmove
    }
  }
  return(oneaway)
}
options <- list()
for (i in 2:9){
  for (n in 2:7){
    adjacent <- oneawayfrom(i,n)
    cell_key <- as.character(numbmatrix[i,n])
    options[[cell_key]] <- adjacent
  }
}

pathmaker <- function(current_path) {
  if (length(current_path) == 48) {
    return(list(current_path))
  }
  last_element <- current_path[length(current_path)]
  all_paths <- list()
  for(i in seq_along(options[[as.character(last_element)]])){
    adjacent_number <- options[[as.character(last_element)]][i]
    if (!(adjacent_number %in% current_path)){
      # 递归收集子路径
      sub_paths <- pathmaker(c(current_path, adjacent_number))
      all_paths <- c(all_paths, sub_paths)
    }
  }
  return(all_paths)
}

# 直接调用函数获取所有路径
storepaths <- pathmaker(current_path=c(numbmatrix[2,2]))

优势： #

• 完全不依赖全局变量，所有数据通过函数返回值传递，避免作用域冲突
• 最终storepaths直接存储所有路径，可直接用storepaths[[i]]调用第i条路径

内容的提问来源于stack exchange，提问作者Stephen Dorn