2. (15 points) News from Cambridge, for those of you far away: every night, snow falls and covers all the sidewalks. Every morning, the city's lone snow shoveler, Pat, is tasked with clearing all the sidewalks of snow. Proper snow-shoveling technique requires that sidewalks 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 doesn't require any more walking than necessary at 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.)