Generic Byte Swap with void Pointers and memcpy

Write one swap function that works for any type, then use it on three of them.

void gswap(void *a, void *b, size_t size) must exchange the size bytes at a with the size bytes at b, moving them with memcpy through a malloc'd scratch buffer that it frees before returning.

Read from stdin, in this order: two integers x and y; two doubles d1 and d2; five integers into an array; two indices i and j (0-based, always valid).

Swap x with y, d1 with d2, and arr[i] with arr[j] — every swap through gswap, with sizeof giving the size.

Print exactly three lines: "ints: " then the two integers; "doubles: " then the two doubles with exactly 2 decimal places; the five array values. Values on a line are separated by single spaces.

Sample input:
3 7
2.50 9.75
10 20 30 40 50
0 4

Free the memory you allocate before the program ends — this question checks for memory leaks.