Is there a way that can change {3, 5, 3, 6} to {3, 5, 6} with a function? I checked all the arduino forums but they don't give the answer i need (just delete 1 item from an array with a function like delete(myArray, 2)).

2 Answers 2


There is no such concept in C. Arrays are a fixed size and that size can never be changed. You can't "delete" an entry. You can replace one with something else, and you can introduce the concept of a variable that says how many entries the array has, but you can't delete one.

So you could:

  • Keep a count of how many entries are in the array
  • Shuffle down all the entries one space so the unused one is at the end
  • Decrement the count of entries

So in your example {3, 5, 3, 6} becomes {3, 5, 6, 6} and your "count" holds 3 to say the first three entries are valid and to ignore the last.

Alternatively you can introduce the concept of "end of array". C strings do this with the NULL character (0). Anything before that character is valid, and anything from that character onwards is ignored. So say you nominated the value -1 to be "end of array" you could have, after again shuffling down the values: {3, 5, 6, -1}.

You could also have -1 (or whatever you chose) indicating an "invalid" entry, so your array would be {3, 5, -1, 6} and you would ignore the -1 entry in your code.

  • Using an invalid value (vs. an end-of-array value) saves shuffling values to over-write the vacated space, but adds some overhead in that array indexing would no longer work as expected but would require walking the array and counting valid values until the i-th one. Some applications may benefit (those that just store data but don't index to it, or not often, anyway), vs. those that do a lot of indexing but not much deleting.
    – JRobert
    Commented Jul 7, 2020 at 17:09

In C++, arrays are fixed-length data structures. There is no way you could remove an item. You could replace it with an invalid item, though.

  • So is there a data array-like type witch can be modifiable?
    – Nobert
    Commented Jul 7, 2020 at 15:33
  • Dynamic objects are not a good idea on a memory-starved device like an Arduino. Come up with a "this space intentionally left blank" value and store that into a location to remove an item. (0 and -1 are common choices for an empty entry, as Majenko mentions in their answer.)
    – Duncan C
    Commented Jul 7, 2020 at 15:49

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