Linear-time stack algorithm for largest rectangle in histogram:
for i = 0 to n do
let h = if i = n then 0 else heights.(i) in
while top-of-stack's height > h do
pop the top, compute its max-width rectangle:
width = (no-stack ? i : i - prev_top - 1)
area = height * width
update best
done;
if i < n then push i
done
Sentinel pass at i=n with h=0 flushes the remaining stack.
For [2; 1; 5; 6; 2; 3], bars at indices 2 (h=5) and 3 (h=6) form
a width-2 rectangle of height 5 = 10.
Tests guarded patterns with `when` inside while-cont-flag, nested
`match !stack with | [] -> i | t :: _ -> i - t - 1` for width
computation.
178 baseline programs total.
giles
609205b551