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

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: