This line of code wont work as intended, because the data type used to store the expression is integer, resulting in integer overflow in case of being greater than INT_MAX.
if(y*10+modulo>INT_MAX) return 0;
This other line executes perfectly when same edge case is encountered. Where y,j are integers, and a is a vector of integers. What data type is used to store this second expression?
if( y+a[i]*pow(10,j)>INT_MAX) return 0;
Additional context: In both cases reversing an integer is attempted, a[i] storing the digits of input number in reverse order, and j starting from size of a -1
To avoid confusion about the -1, a 3 digit number ex 123 can be written like this 1 * 10^2 + 2 * 10^1 + 3*10^0
I tried the first two things you do before coming here, asking google and ai about this case.
The "secret" is the call to pow; despite being given integer arguments, it only has float-type variants (in this case, I believe it defaults to double). This causes the entire expression to use a floating-point type, which does have a larger range than int.