w / r [terminology]

Terminology¶

Usage¶

• Use w for a write index and r for a read index in compact in-place algorithms.
• w marks where the next retained value is written.
• r marks the element currently being inspected.
• This pair is preferable to generic i and j because it expresses data flow.

w = 0

for r in range(n):
    if nums[r] != 0:
        nums[w], nums[r] = nums[r], nums[w]
        w += 1