• C

Convert array of integers to single int

Suppose I have an array of single-digit, base 10 integers, like:

int intarray = { 2 , 5, 7 };

Is there a way I can convert this into a single int, with a value of 257?
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You mean like

int a2int(int* arr, size_t sz) {

int ret = 0;

 for (int i = 0; i < sz; ++i) {

  ret *= 10;

  ret += arr[i];

return ret;


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Hi chsalvia,

Could you please post what you have tried and we can help you understand what you are doing wrong or help you out with the parts you find difficult.

You could do it.

Firstly, each array represents a power of ten.

So lets say you have an int array [1 2 3 4 5]

this means, your integer will be ( working backwards ):
(5 * 10 ^ 0) + (4 * 10 ^ 1) + (3 * 10 ^ 2) + (2 * 10 ^ 3) + (1 * 10 ^ 4)

so if you see the pattern you could write a simple for loop which iterates through the int array, multiply it by it's 10's coefficient, and add it to the total sum.

Good luck with it.
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