Using a loop, rearrange a vector of integers such that the odd numbers appear at the beginning, and even numbers at the end. The order within each group should be preserved.

Examples:

Input:  v = [1, 0, 2, 9, 3, 8, 8, 4]
Output: w = [1, 9, 3, 0, 2, 8, 8, 4]

Input:  v = [2
             7
             0
             3
             2]

Output: w = [7
             3
             2
             0
             2]

Input:  v = []
Output: w = []