Name the left edge of a window
Updated
L is the leftmost index in the window. It is an index, not a value. a[L] is the cell sitting at that index.
What to focus on
L is inclusive. Every index < L is outside. L is not a[L].
Worked examples
left of a middle window
a = [4, 1, 9, 1], L=1 R=3- left edge is index 1
- a[1] = 1
- index 0 is outside
Result: L = 1
left of the whole array
a = [4, 1, 9], L=0 R=2- left edge is index 0
- a[0] = 4
Result: L = 0
left of a string window
s = "abca", L=2 R=3- left edge is index 2
- s[2] = c
Result: L = 2
Try it
Write leftEdge(L, R). L is the left index of the window. R is the right index. The window includes a[L] through a[R]. L is inclusive. Return L. Do not confuse L with a[L]. On a=[4, 1, 9, 1] with (1, 3) and (0, 3); a=[4, 1, 9] with (0, 2); s="abca" with (2, 3).
a (or s) is nonempty. 0 ≤ L ≤ R < n.