News from Cambridge, for those of you far away: every night, snow falls and covers all the sidewalks. Every morning, the citys lone snow shoveler, Pat, is tasked with clearing all the sidewalks of snow. Proper snow-shoveling technique requires that side walks on opposite sides of the same street be shoveled in opposite directions. (Every street has sidewalks on both sides.) Give an algorithm to find a snow-shoveling path for Pat that doesnt require any more walking than necessaryat most once per sidewalk. (If you have to assume anything about the layout of the city of Cambridge, make it clear!) (Your algorithm should work for any city, not just the Cambridge in which Harvard is.)