  The running maximum-minimum (max-min) filter computes the maxima and minima
over running windows of size w. This filter has numerous applications in signal
processing and time series analysis. We present an easy-to-implement online
algorithm requiring no more than 3 comparisons per element, in the worst case.
Comparatively, no algorithm is known to compute the running maximum (or
minimum) filter in 1.5 comparisons per element, in the worst case. Our
algorithm has reduced latency and memory usage.
