用1至9组成的四位数字没有重复,全部写出来.（能写多少写多少）
问题描述：
用1至9组成的四位数字没有重复,全部写出来.（能写多少写多少）
答
1230,1234,1235,1236,1237,1238,1239,1240,1245,1246,1247,1248,1249,1230,1234,1235,1236,1237,1238,1239,1240,1245,1246,1247,1248,1249,1250,1256,1257,1258,1259,1260,1267,1268,1269,1270,1278,1279,1280,1289,...