Assume you have a swap routine in place for doubles. Write a routine calls swap that reverses the entries in an array of doubles. Use this function declaration. void reverse( double a, int size); Carry out your reversal in place, do not make a local copy of the array

Question

What will be an ideal response?

Answer 1

The answer is in bold face embedded in a complete test program.

```
include const int SIZE = 10;
void swap(double& lhs, double& rhs) { double tmp = lhs;
lhs = rhs;
rhs = tmp;
}

void reverse( double a[], int size)
{
using namespace std;

for (int i = 0; i < (size - 1)/2; i++)
swap(a[i], a[size - i - 1]);
}

int main()
{
using namespace std;
double foo[SIZE] = {0,1,2,3,4,5,6,7};

for (int i = 0; i < SIZE; i++)
cout << foo[i] << " ";
cout << endl;

reverse(foo, SIZE);

for (int i = 0; i < SIZE; i++)
cout << foo[i] << " ";
cout << endl;
}
```

Note the (size - 1)/2 in the for loop test. If this is size-1, the routine reverses the array twice, undoing the reverse.