How to copy a two-dimensional array in Kotlin?

Question

This method works fine. However, I think it is not functional.

fun getCopy(array: Array<BooleanArray>): Array<BooleanArray> {
    val copy = Array(array.size) { BooleanArray(array[0].size) { false } }
    for (i in array.indices) {
        for (j in array[i].indices) {
            copy[i][j] = array[i][j]
        }
    }
    return copy
}

Is there a more functional way?

miensol · Accepted Answer · 2016-11-07T12:57:58.647

17

You can make use of clone like so:

fun Array<BooleanArray>.copy() = map { it.clone() }.toTypedArray()

or if you'd like to save some allocations:

fun Array<BooleanArray>.copy() = arrayOfNulls<ByteArray>(size).let { copy ->
    forEachIndexed { i, bytes -> copy[i] = bytes.clone() }
    copy
} as Array<BooleanArray>

or even more concise as suggested by @hotkey:

fun Array<BooleanArray>.copy() = Array(size) { get(it).clone() }

edited Nov 07 '16 at 12:57

answered Nov 07 '16 at 11:07

miensol

39,733
7
116
112

8

Another allocation-efficient implementation: `fun Array.copy() = Array(size) { get(it).clone() }` – hotkey Nov 07 '16 at 12:24

score -1 · Answer 2 · answered Feb 18 '18 at 12:02

-1

What about using copyOf()?

val copyOfArray = array.copyOf()

Returns new array which is a copy of the original array

Reference here

answered Feb 18 '18 at 12:02

mxcoder

7
2

7

the sample code in the question indicates that a deep copy is required. this code creates a shallow copy. – hoijui Aug 03 '18 at 20:52
1

This keeps references of internal array – Moaz Rashad Apr 12 '22 at 00:46

How to copy a two-dimensional array in Kotlin?

2 Answers2

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