求从小到大和从大到小排序
给出任意字串，求从小到大和从大到小排序？字串是由N个数字加‘/’组合在一起的如a='15/464/4694/1/1456/02/1648/01/16644/9/865/461/005'会得出
a1='1/1/2/5/9/15/461/464/864/1456/1648/4694/16644'
a2='16644/4694/1648/1456/864/464/461/15/9/5/2/1/1'
a3='01/1/02/005/9/15/461/464/864/1456/1648/4694/16644'
a4='16644/4694/1648/1456/864/464/461/15/9/005/02/1/01'
如何快速得到a1,a2,a3,a4
