Array Subscript is out of range. What does that mean? Help

[mew123mew]

I have to write a program where i am throwing a party, but i can't invite all my friends

So I must number your friends 1, 2, . . . , K and place them in a list in this order. Then perform m rounds. In each round, use a number to determine which friends to remove from the ordered list.
The rounds will use numbers r1, r2, . . . , rm. In round i remove all the remaining people in positions that are multiples of ri (that is, ri , 2ri , 3ri , . . .) The beginning of the list is position 1.
Output the numbers of the friends that remain after this removal process.

Input Specification
The first line of input contains the integer K (1 ≤ K ≤ 100). The second line of input contains
the integer m (1 ≤ m ≤ 10), which is the number of rounds of removal. The next m lines each
contain one integer. The ith of these lines (1 ≤ i ≤ m) contains ri ( 2 ≤ ri ≤ 100) indicating that
every person at a position which is multiple of ri should be removed.

What I have so Far:

Turing:

var x :int %number of guests var y :int %number of rounds of removal var z :int %removal var number: flexible array 1..0 of int var removal: flexible array 1..0 of int get x % get number of guests new number, x for i: 1..x number(i) := i end for get y%get rounds of removal for a: 1..y get z removal(a) := z end for for i:1..x if i mod removal(z) = 0 then     new number, upper (number) - 1 end if end for for a: 1..x     put number(a) end for

Whenever I run it, it says Array Subscript is out of range. Why does it not work?

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Mod Edit: Please wrap your code in syntax tags to preserve indentation.

[Zren]

First try debugging the variables you know are causing problems. Since you're getting the error on removal (a) := z, add some debugging output just before that to get an idea of the state of everything that's causing the error.

Turing:

for a : 1 .. y     get z     put "a = ", a     put "upper(removal) = ", upper (removal)     removal (a) := z end for

Output:

code:

a = 1 upper(removal) = 0

[mew123mew]

Thank you but I still don't understand how to fix it.

[Zren]

You resized the numbers flexible array with the new statement after you obtained the size from user input, but you didnt do the same for the removal flexible array.

[mew123mew]

Oh Thanks!

I was wondering is it possible to remove a specific element in a array. For example in my code i want to remove only, the element that can be divided by z.

[Raknarg]

You have to shift all the elements bigger than it down by one. When you resize downwards, it just removes the last elements in the array.

[mew123mew]

How do you do that?

[Zren]

Turing:

View.Set ("text") var arr : array 1 .. 5 of int := init (1, 2, 3, 4, 5) var indexToRemove := 3 % Shifting to the left (copy the element to the right of it) % arr(3) := arr(4) % arr(4) := arr(5) % ...and so on to the end of the array % You should have noticed the pattern of copying arr(i) := arr(i + 1) % arr(5) is the last element and should be removed by resizing the array to not include it. % Shift (TODO) % Here's how you can iterate the pairs of indexes. for i : indexToRemove .. upper (arr) - 1     put arr (i), " ", arr (i + 1) end for % Remove trailing element by resizing the array 1 size smaller (TODO) % ...

[mew123mew]

Thanks, but now i have another problem. I need to remove multiple elements at the same time.

[Raknarg]

Welk you can use this method, just do it more than once at a time. If you need to remove 5 elements, use this method 5 times for each element to be removed.

[mew123mew]

The problem for me is I need to remove all the elements for which that has a subscript that can be divided by 2. So I did:

code:

for a : 1 .. upper (people) %2         put people (a)         if (people (a) mod remove = 0) then             for b : remove .. upper (people) - 1 %3                 people (b) := people (b + 1)             end for %3                 decrease := decrease + 1             for z : 1 .. guest                 put people (z)             end for         end if     end for %2

The thing is, it keeps on removing the element that has a subscript of 2, and not any others

[Insectoid]

Is people(a) the name of the person or the subscript of that person?

You seem to have the right idea, but you're mixing up your variables.

[mew123mew]

people(a) is the subscript

[Zren]

Mutating an array while iterating it is generally a bad idea.

If you remove/shift the elements while iterating, you'll end up skipping elements.

Turing:

proc printIntSubArray (arr : array 1 .. * of int, s : int, e : int)     for i : s .. e         put "[", arr (i), "]" ..     end for     put "" end printIntSubArray proc printIntArray (arr : array 1 .. * of int)     printIntSubArray (arr, 1, upper (arr)) end printIntArray proc shift (var arr : array 1 .. * of int, startIndex : int)     for i : startIndex .. upper (arr) - 1         arr (i) := arr (i + 1)     end for end shift View.Set ("text") var arr : array 1 .. * of int := init (1, 2, 3, 4, 5, 6, 7, 8, 9) printIntArray (arr) for i : 1 .. upper (arr)     put skip     put "i = ", i     put "arr(i) = ", arr (i)     printIntArray (arr)     put "shift (arr, ", i, ")"     shift (arr, i)     printIntArray (arr) end for

code:

[1][2][3][4][5][6][7][8][9] i = 1 arr(i) = 1 [1][2][3][4][5][6][7][8][9] shift(arr, 1) [2][3][4][5][6][7][8][9][9] i = 2 arr(i) = 3 [2][3][4][5][6][7][8][9][9] shift(arr, 2) [2][4][5][6][7][8][9][9][9] i = 3 arr(i) = 5 [2][4][5][6][7][8][9][9][9] shift(arr, 3) [2][4][6][7][8][9][9][9][9] i = 4 arr(i) = 7 [2][4][6][7][8][9][9][9][9] shift(arr, 4) [2][4][6][8][9][9][9][9][9] ...

Notice how we skipped some of the elements?

One way to "filter" elements out of an array would be to keep track of the number of kept elements, and move them into position as you iterate through. Then at the end, resize the array.

code:

[1][2][3][4][5][6][7][8][9] i = 1 arr(i) = 1 keep = false newSize = 0 [1][2][3][4][5][6][7][8][9] i = 2 arr(i) = 2 keep = true newSize = 1 [2][2][3][4][5][6][7][8][9] [2] i = 3 arr(i) = 3 keep = false newSize = 1 [2][2][3][4][5][6][7][8][9] [2] i = 4 arr(i) = 4 keep = true newSize = 2 [2][4][3][4][5][6][7][8][9] [2][4] ... i = 9 arr(i) = 9 keep = false newSize = 4 [2][4][6][8][5][6][7][8][9] [2][4][6][8] [2][4][6][8]