2011ACM亚洲区域赛北京赛区-试题.pdfVIP

A. Qin Shi Huangs National Road System A. Qin Shi Huangs National Road System AA..QQiinnSShhiiHHuuaannggssNNaattiioonnaallRRooaaddSSyysstteemm Description Description DDeessccrriippttiioonn During the Warring States Period of ancient China(476 BC to221 BC), there were seven kingdoms in China they were Qi, Chu, Yan, Han, Zhao, Wei and Qin. Ying Zheng was the king of the kingdom Qin. Through 9 years of wars, he finally conquered all six other kingdoms and became the first emperor of aunified China in 221 BC.That was Qin dynasty the first imperial dynasty of China(not to be confused with the Qing Dynasty, the last dynasty of China). So Ying Zheng named himself Qin Shi Huang because Shi Huang meansthefirst emperor in Chinese. Qin Shi Huang undertook gigantic projects, including the first version of theGreat Wall of China, the now famous city-sized mausoleum guarded by a life-sized Terracotta Army, and a massive national road system.There is astoryabout the roadsystem: There were n cities in China and Qin Shi Huang wanted them all be connected by n-1roads, in order that he could go to every city from the capital city Xianyang. Although Qin Shi Huang was a tyrant, he wanted the total length of all roads to be minimum,so that the road system may not cost too many peoples life. A daoshi (some kind of monk) named Xu Fu told Qin Shi Huang that he could build a road by magic and that magic road