Given an array of integers e, arrange the elements in it so that:
e[0] ≤ e[1] ≥ e[2] ≤ e[3] ≥ e[4] ...
The elements in e need not be unique (they may be repeated)
5 2 1 7 9 8 -> 1 ≤ 7 ≥ 5 ≤ 9 ≥ 2 ≤ 8 or 2 ≤ 5 ≥ 1 ≤ 9 ≥ 7 ≤ 8 or ...
1 2 3 4 5 6 -> 1 ≤ 3 ≥ 2 ≤ 5 ≥ 4 ≤ 6 or ...
-2 3 3 -3 -> 3 ≤ 3 ≥ -3 ≤ -2 or -2 ≤ 3 ≥ -3 ≤ 3 or ...
sort : O(n logn) swapping : O (n)
O(n log n)