The error reads:
request for member \'begin\', \'end\' in \'arr\' which is non class type int[5], unable to deduce from expression error.
Quite late but I think it's worth to mention that:
void findavgTime(int n)
{
int wt1[n];
fill_wt(wt1,n); //Any method that puts the elements into wt1
int wt2[3];
int sum = accumulate(begin(wt1), end(wt1), 0); // Fails but wt2[3] will pass. Reason: variable-sized array type ‘int [n]’ is not a valid template argument)
}