Start both pointers on the same cell
Updated
Starting together means L = R at the same index, usually 0. The pair is one cell until one pointer moves. Same-direction scans grow a gap from this zero-gap start.
What to focus on
After init, L == R and that index is in range. Reading a[L] and a[R] is the same slot twice until they split.
Worked examples
start 0
a = [4, 1, 9]- L ← 0
- R ← 0
- both sit on 4
Result: L=0, R=0
only cell
a = [7]- the only index is 0
- L and R both land there
Result: L=0, R=0
empty
a = []- no cell to share
- do not set L=R=0
Result: no L, R
Try it
Write startTogether(a). a is an array of integers. L and R are indices that share one in-range cell. Set L = R, usually 0. Print L and R. Return nothing. On [4, 1, 9], [4, 1, 9, 1], and [7], both pointers share index 0.
a may be empty. Length ≥ 1.