I have an array A [8] = {0}; And another array B[20] = {0};
I want to move all the values from B[12...20] to A[0...8]. How can i exactly change the indices? is there a formula? So B[12] -->A[0] B[13] -->A[1]
Thank you.
4 Answers
Use std::copy. It works for user defined types too:
std::copy(B+12, B+20, A);
or, in c++11,
std::copy(std::next(B,12), std::end(B), std::begin(A));
Comments
You should use std::copy here, which will work correctly no matter the type of elements in your arrays (speaking of which, you don't show that type -- the question has invalid syntax).
std::copy(B + 12, B + 20, A);
Comments
Simply write a loop
int offset = 12;
int lenA = 8;
for(int i=0; i < lenA; i++) {
A[i] = B[i+offset];
}
Comments
memcpy(A, B + 12, 8 * sizeof(A[0])); should do the trick.
Assuming A and B are both the same type.
6 Comments
Hani Goc
hi @dunc is there a way to do it using for loop?
Anshul
It won't copy memcpy would copy number of bytes. If it is an integer or some other object - byte count would differ
dunc123
I'd actually recommend the
std::copy answer from Jon, since you are using C++.Hani Goc
I actually wanted to see how I can switch between the incides using the for loop
jcoder
This will only work if the arrays are of basic C compatible types. Use std::copy, it is safer, it indicated the intent better (you are copying elements, NOT memory), and very likely compiles down to a memcpy where is't safe to do so anyway
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B[20]is out of bounds. You probably meanB[12...19].