C# Challenge Variable value exchange

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I recently made a very simple challenge :

Swap the value of two variables without using a third variable.

int a = 5;
int b = 3;

a += b;     // a = 8
b = a - b;  // b = 5;
a -= b;     // a = 3;

It is simple because they are arithmetic operations.

Yet I was thinking how to do it if they were strings.

string a = 'Stack';
string b = 'Overflow';

I even thought of some solutions, but these apply to weak typing languages :

Example JS

var a = 'Stack';
var b = 'Overflow';

a = a+'|'+b;      // a = 'Stack|Overflow';
a = a.split('|'); // a = ['Stack', 'Overflow'];

b = a[0];  // b = 'Stack';
a = a[1];  // a = 'Overflow';

How could I solve this challenge with string?

c# variables typing

  • You have some restraint of what you can do?

  • @bigown no, just can’t use another variable.

  • So I don’t care, these things don’t lead anywhere :P Doing it in a worse way when you can do it the best way I don’t like. The existing answer is sufficient.

  • @bigown The true test (with ints) had a mathematical purpose, so it made a certain sense :P

  • @jbueno exactly, although I think it would be better done with bit operator. This is a crazy thing to do. It is quite slow and destructive of memory :)

  • @bigown I’m not a great connoisseur of C#, I even thought of some more methods by converting to binary, but then one would have to change the type of variable. I know you are a great connoisseur, I would like your participation, for learning purposes.

  • 1

    You have nothing to do with this restriction. You may have a better solution than this, but none will be good. The obvious and good solution is to use a temporary variable. Unlike an integer that is small in size and the full copy does not generate large overhead, string generates different values. So you’re not creating a new variable, but is creating new values, which is much worse. If there was a reason to do this I would understand, but artificial restraint makes it a curiosity without practical sense.

  • I understood, in case I would be using more memory than to do with a helper.

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2 answers

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There are many ways to do it.

The first thing I thought was

string a = "Teste";
string b = "Overflow";

a += "|" + b;

b = a.Split('|')[0];
a = a.Split('|')[1];

WriteLine($"a = {a} - b = {b}");

The exit will be:

a = Overflow - b = Test

See working on .NET Fiddle

  • Very good, I did not contemplate this. :/

  • I see badly or this is no more than the "translation" to C# of the example, in JS, presented in the question?

  • I hadn’t been paying attention, but it is. I believe this is no @ramaral problem

  • I did not see as a problem I just thought that the AP should not have been content with an answer that boils down to the "translation" of what was in the question.

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Following exactly the same idea as jbueno, but using the tricks of weak typing languages, where in C# these advantages can be achieved with Dynamic.

dynamic a = "Teste";
string b = "Overflow";

a = (a + "|" + b).Split('|');

b = a[0];
a = a[1];

WriteLine($"a = {a} - b = {b}")

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