内螺旋覆盖搜索的一个算法实现，运行为plotdmap（a,b,c,d）a,b,c,d为数字，a,b为栅格地图的长宽，c为搜索目标的数量，位置自动随机出现杂地图上，d为搜索车辆的数量，位置分布在地图最外围。-Cover a spiral search algorithm, run for the plotdmap (a, b, c, d) a, b, c, d for the number, a, b for the grid map of the length and width, c is the number of search targets, location Auto randomly mixed map, d the number of vehicles for the search, location map of the distribution in the outermost.