如何从输入表 Lua 创建输出表？

Question

我需要帮助来修复我的代码。因为我最后一个失败了，没有 9。

问：填写 if_then_elseif() 函数以使用 for 循环和 if then else 语句创建所需的数组。 目标是根据以下对应关系创建一个与输入表等效的输出表 {“1”、“2”、“3”、“4”、“5”、“6”、“7”、“8”、“9”} =>> {“a”、“b”、“ c”、“d”、“e”、“f”、“n”、“n”、“n”} ]]

require "testwell"

function foo(arg)
  --arg is the table of numbers
  local out = {}
  local n = #arg
  -- Put your code between here **************** 
 for i = 1,#arg,1 do
  if i==1 then out[i] = "a"
    elseif i==2 then out[i] = "b"
     elseif i==3 then out[i]= "c"
      elseif i==4 then out[i] = "d"
       elseif i==5 then out[i]= "e"
        elseif i==6 then out[i] = "f"
         elseif i==7 then out[i] = "n"
          elseif i==8 then  out[i]= "n"
           elseif i==9 then out[i] = "n"
          else print("invalid input")
            
end 
end
  -- and here **********************************
  return out
end

is(foo({1,2}), {"a", "b"}, 'numbers to letters 1')
is(foo({1,2,3}), {"a", "b", "c"}, 'numbers to letters 2')
is(foo({1,2,3,4}), {"a", "b", "c", "d"}, 'numbers to letters 3')
is(foo({1,2,3,4,5}), {"a", "b", "c", "d", "e"}, 'numbers to letters 4')
is(foo({1,2,3,4,5,6}), {"a", "b", "c", "d", "e", "f"}, 'numbers to letters 5')
is(foo({1,2,3,4,5,6,7}), {"a", "b", "c", "d", "e", "f", "n"}, 'numbers to letters 6')
is(foo({1,2,3,4,5,6,7,8}), {"a", "b", "c", "d", "e", "f", "n", "n"}, 'numbers to letters 7')
is(foo({1,2,3,4,5,6,7,8,9}), {"a", "b", "c", "d", "e", "f", "n", "n", "n"}, 'numbers to letters 8')
is(foo({9,8,7,6,5,4,3,2,1}), {"n", "n", "n", "f", "e", "d", "c", "b", "a"}, 'numbers to letters reversed')
report()
``````````````````````
the output i received is 
`````````
Program 'lua.exe' started in 'C:\Users\Marian\Downloads\ZeroBraneStudio\myprograms' (pid: 6032).
ok 1 - numbers to letters 1
ok 2 - numbers to letters 2
ok 3 - numbers to letters 3
ok 4 - numbers to letters 4
ok 5 - numbers to letters 5
ok 6 - numbers to letters 6
ok 7 - numbers to letters 7
ok 8 - numbers to letters 8
not ok 9 - numbers to letters reversed
#     Failed test 'numbers to letters reversed'
#     in ...\ZeroBraneStudio\myprograms\290-A2\05-e-if then else.lua at line 54.
#          got: {"a", "b", "c", "d", "e", "f", "n", "n", "n"} (table)
#     expected: {"n", "n", "n", "f", "e", "d", "c", "b", "a"} (table)
1..9 # Looks like you passed 8 and failed 1 test of 9 (8/0/9).
Program completed in 0.17 seconds (pid: 6032).
`````````````````````

Answer 1

我的个人建议：

function foo( arg )
    --arg is the table of numbers
    local map = {'a', 'b', 'c', 'd', 'e', 'f', 'n', 'n', 'n'}
    local out = {}
    local n = #arg -- not needed.
  -- Put your code between here ****************
    for key, value in pairs( arg ) do -- note the associative arg is also handled.
        out[key] = map[value] or print 'Invalid input' -- no need of if's.
    end
    -- and here **********************************
    return out
end

但是如果你必须使用if的angarg是一个纯索引数组：

function foo( arg )
    --arg is the table of numbers
    local out = {}
    local n = #arg
  -- Put your code between here ****************
    for i = 1, n do
        if arg[i] == 1 then out[i] = 'a'
        elseif arg[i] == 2 then out[i] = 'b'
        elseif arg[i] == 3 then out[i] = 'c'
        elseif arg[i] == 4 then out[i] = 'd'
        elseif arg[i] == 5 then out[i] = 'e'
        elseif arg[i] == 6 then out[i] = 'f'
        elseif arg[i] == 7 or arg[i] == 8 or arg[i] == 9 then out[i] = 'n'
        else print 'Invalid input' end
    end
    -- and here **********************************
    return out
end

P.S.我希望你的老师没有阅读 StackOverflow。