Reverse character array using recursion

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Todd Wilson
Todd Wilson 2017-10-17
回答： Selman Baysal 2022-1-8
I'm having trouble creating a function that would reverse a character array using recursion. For example, I want my function to return 'py' when inputting "yp". My overall code doesn't seem right though.
function array2 = charReversal(array1)
if array1==0
return;
else
array2=chsrReversal(reverse(array1,array1-1));
disp(array2)
end

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采纳的回答

Guillaume
Guillaume 2017-10-17
I assume this is homework so I'm hesitant even answering the question since the whole purpose of the exercise is to make you think of a recursive algorithm.
It is trivial to reverse a string by recursion: take the first element of the string, put it at the end of the string returned by calling the recursive function with the rest of the string (from character 2 to end). The recursion stops when the function receives only 1 character.
  2 个评论
Todd Wilson
Todd Wilson 2017-10-17
Yes this is homework, but I am stuck. Your suggestion is a good one to try and I will use it soon. I'm wondering what I should put for "if array1==....."?
Guillaume
Guillaume 2017-10-17
编辑：Guillaume 2017-10-17
There is no if array1 == test required. As I wrote, "The recursion stops when the function receives only 1 character". That is what you have to test for.

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更多回答（5 个）

Anuj Kumar
Anuj Kumar 2020-10-9
instead of using v=[v(end) reversal(1:end-1)] which won't satisfactorily on large arrays,i would recommend this piece of code
function v=reversal(v)
if(length(v)>1)
d=length(v);
x=0;
if mod(d,2)==0
x1=d/2;
x2=x1+1;
m=v(1:x1);
n=v(x2:end);
v=[reversal(n),reversal(m)];
else
x1=fix(d/2);
x2=x1+2;
m=v(1:x1);
mid=(x1+1:x1+1);
n=v(x2:end);
v=[reversal(n),v(mid),reversal(m)];
end
end
end
Saurabh Wani
Saurabh Wani 2020-8-17
i have try this code and it gives reversal of array elements using recursive method
function w=reversal(v)
s=length(v)
if s==1
w=v
else
w=[v(end) reversal(V(1:s-1))]
end
  2 个评论
Hazem Ahmed
Hazem Ahmed 2020-8-19
编辑：Walter Roberson 2020-8-20
could you explain what are you doing in this line?
w=[v(end) reversal(V(1:s-1))]
Piyush Gupta
Piyush Gupta 2020-9-10
编辑：Piyush Gupta 2020-9-10
its an array, you can declare without comma too.

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KSSV
KSSV 2017-10-17
You can either use fliplr or give indices in reverse.
str = 'py' ;
fliplr(str)
str(end:-1:1)
  4 个评论
显示 2更早的评论
Todd Wilson
Todd Wilson 2017-10-17
For array2 = charReversal(array1), shouldn't there be a function such as reverse? Also, I need the code to be in recursion.
KSSV
KSSV 2017-10-17
Ohh..why recursion needed? That case you may add it. But don't use str.

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ambuj aman
ambuj aman 2020-9-15
function out = reversal(in)
if length(in) <= 1
out = in;
else
out = [ reversal(in(2:end)) in(1) ];
end
end
Selman Baysal
Selman Baysal 2022-1-8
I solve this problem by removing first and last elements in the vector until one or zero element remains.
function w = reversal(v)
if length(v) <= 1
w = v;
else
v1 = v(end); v(end) = [];
v2 = v(1); v(1) = [];
w = [v1 reversal(v) v2];
end

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