Getting user input for an array

Question

I try to create an array. The size of it depends on the user's input. But how can I do it? or should I use string or vector instead?

I am new to C++. When I googled the problem, I still didn't get it. I tried the following code but it was not working.

const int t;
cin >>t;
double myarrary[t]={};

but my friends code works.

cin >> num;
int px[num]={};

Thank you

Open your C++ book to the chapter that introduces you to the C++ library, and the std::vector template, and all will be explained. "Googling" is not a very good way to learn C++. The best way to do so is by learning from a good C++ book. — Sam Varshavchik
– Sam Varshavchik, Commented Mar 30, 2019 at 2:00

Maxim Egorushkin · Accepted Answer · 2019-03-30 02:00:08Z

3

Variable length arrays like double myarrary[t] where t is a run-time value are a C feature. It is not in C++ standard, but some compilers do support that.

Use std::vector for portability.

answered Mar 30, 2019 at 2:00

Maxim Egorushkin

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5 Comments

Www Over a year ago

but i set t as constant. Shouldn't it be treated as a constant?

L. F. Over a year ago

@Www Working on some compilers doesn’t mean that you should write such code. Conformance to the standard does.

user9254539 Over a year ago

@Www How can it be a constant if you're reading user input into it after it was declared? By definition, the value of a const variable has to be initialized when it is declared and can't change after that. Also, array sizes need to be compile-time constants (the value is known during compile time), not just constant after the declaration.

user9254539 Over a year ago

@L.F. Conformance to the standard doesn't necessarily mean the code is good either.

L. F. Over a year ago

@FeiXiang Oh yes! Definitely! It was only meant to be a comparison, but I worded it too ambiguously ...

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