将若干城市的信息输入一个带头结点的单链表，结点中的城市信息包括城市名称，城市的位置坐标，要求：（1）给定一个城市名，返回位置坐标；（2）给定一个位置坐标p和一个距离d，返回所有与p得距离小于等于d的城市。-Enter the number of towns and cities take the lead in a single linked list nodes, nodes in the city information including city name, city location coordinates requirements: (1) Given a city name, returned location coordinates　(2) Given a location coordinates p and a distance d, to return all p less than or equal d was the distance the city.