两个路径搜索的经典算法，希望对学这方面的人有用-two classic algorithms of pathfinding

产生两组小球，每组小球有不同的目的地，两组球同时出发，相遇并互相碰撞最终到达终点。-Produce two small balls, each ball has a different destination, two balls on the same flight, meet and collide with each other eventually reach the end.