Reverse array elements in Julia – reverse(), reverse!() and reverseind() Methods

• Last Updated : 01 Apr, 2020

The `reverse()` is an inbuilt function in julia which is used to reverse the specified vector v from start to stop.

Syntax:
reverse(v, start, stop)
or
reverse(A; dims::Integer)

Parameters:

• v: Specified vector.
• start: Specified starting value.
• stop: Specified stopping value.
• A: Specified array.
• dims::Integer: Specified dimensions.

Returns: It returns a reversed copy of the vector.

Example 1:

 `# Julia program to illustrate ``# the use of reverse() method``  ` `# Getting the reversed copy of ``# the specified vector.``A ``=` `Vector(``2``:``8``)``println(reverse(A))``println(reverse(A, ``3``, ``6``))``println(reverse(A, ``7``, ``4``))`

Output:

```[8, 7, 6, 5, 4, 3, 2]
[2, 3, 7, 6, 5, 4, 8]
[2, 3, 4, 5, 6, 7, 8]```

Example 2:

 `# Julia program to illustrate ``# the use of reverse() method``  ` `# Getting reversed array in ``# the specified dimension``A ``=` `[``5` `10``; ``15` `20``]``println(reverse(A, dims ``=` `1``))``println(reverse(A, dims ``=` `2``))`

Output:

reverse!()

The `reverse!()` is an inbuilt function in julia which is In-place version of reverse() function.

Syntax:
reverse!(v, start, stop)

Parameters:

• v: Specified vector.
• start: Specified starting value.
• stop: Specified stopping value.

Returns: It returns a reversed copy of the vector.

Example:

 `# Julia program to illustrate ``# the use of reverse !() method``  ` `# Getting the reversed copy of ``# the specified vector.``A ``=` `Vector(``2``:``8``)``println(reverse !(A))``println(reverse !(A, ``3``, ``6``))`

Output:

```[8, 7, 6, 5, 4, 3, 2]
[8, 7, 3, 4, 5, 6, 2]
```

reverseind

The `reverseind()` is an inbuilt function in julia which is used to return the corresponding index in v so that v[reverseind(v, i)] == reverse(v)[i], where i is the given index.

Syntax:
reverseind(v, i)

Parameters:

• v: Specified string.
• i: Specified index.

Returns: It returns the corresponding index in v so that v[reverseind(v, i)] == reverse(v)[i].

Example:

 `# Julia program to illustrate ``# the use of reverseind() method``  ` `# Getting the corresponding index in v``# so that v[reverseind(v, i)] == reverse(v)[i]``V ``=` `reverse(``"Geeks"``)``for` `i ``in` `1``:length(r)``    ``print``(V[reverseind(``"Geeks"``, i)])``end`

Output:

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