How come my arrary won't take a user entered size?Code:void main() { const int size; cout << "Please enter a amount of lights" << endl; cin >> size; int lights[size]; for (int i = 0; i < n; i++) { lights[i] = 1; } }
How come my arrary won't take a user entered size?Code:void main() { const int size; cout << "Please enter a amount of lights" << endl; cin >> size; int lights[size]; for (int i = 0; i < n; i++) { lights[i] = 1; } }
Firstly, size is const. More importantly, standard C++ does not provide for variable length arrays. Use a std::vector instead, e.g.,
Code:#include <iostream> #include <vector> int main() { std::vector<int>::size_type size; std::cout << "Please enter a amount of lights" << std::endl; std::cin >> size; std::vector<int> lights(size, 1); // No need for the init loop any more. // ... do other stuff ... }
Look up a C++ Reference and learn How To Ask Questions The Smart WayOriginally Posted by Bjarne Stroustrup (2000-10-14)
We have not got to vectors in class. I don't know if I can use that I will play with it anyway thanks.
If you cannot use the standard containers, then it implies that you should use new[] and delete[]. If you cannot use that either, then you should create a large enough array, and only use the first size elements of that array.
Look up a C++ Reference and learn How To Ask Questions The Smart Way
Alright I'll see what I can do I'm trying to make a program using recursion to set all of the lights to off (0) when they are initially set to on (1).
Write a function to print the integers from 0 to size-1, having only the current number and the size as the parameters. Then add a parameter for the array of lights and start setting the lights to off instead of printing integers.Alright I'll see what I can do I'm trying to make a program using recursion to set all of the lights to off (0) when they are initially set to on (1).
Alternatively, write a function to print the integers from size-1 to 0, having only the current number as the parameter. Then add a parameter for the array of lights and start setting the lights to off instead of printing integers.
Look up a C++ Reference and learn How To Ask Questions The Smart Way
try like so???
in your lights .cpp
Code:void lights::makeArray(){ int size; cout << "Please enter a amount of lights" << endl; cin >> size; int lights[size]; for (int i = 0; i < size-1; i++) { lights[i] = 1; } }
Nope. That gets the value into size perfectly well, but it declares a variable-length array, which is apparently not standard C++.
(BTW, the for loop should likely have this condition: "i < size".)
laserlight has already supplied a vector example. Here's a dynamic memory allocating one.
The delete statement frees the memory allocated by new, and should be called after you are done using the array. Otherwise you have a memory leak.Code:// after reading int size from the user: int *lights = new int[size]; // ... use the array lights ... delete [] lights;
dwk
Seek and ye shall find. quaere et invenies.
"Simplicity does not precede complexity, but follows it." -- Alan Perlis
"Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
"The only real mistake is the one from which we learn nothing." -- John Powell
Other boards: DaniWeb, TPS
Unofficial Wiki FAQ: cpwiki.sf.net
My website: http://dwks.theprogrammingsite.com/
Projects: codeform, xuni, atlantis, nort, etc.
Also,
http://cpwiki.sf.net/Void_main
Get rid of the void main and use int main.
