如果不考虑顺序（也就是说,1234与4123是等同的）
则每4个一组能组成C8(4)=8*7*6*5/(4*3*2*1)=70组
1234,1235,1236,1237,1238,1245,1246,1247,1248,1256,1257,1258
1267,1268,1278,1345,1346,1347,1348,1356,1357,1358,1367,1368
1378,1456,1457,1458,1467,1468,1478,1567,1568,1578,1678,2345
2346,2347,2348,2356,2357,2358,2367,2368,2378,2456,2457,2458
2467,2468,2478,2567,2568,2578,2678,3456,3457,3458,3467,3468
3478,3567,3568,3578,3678,4567,4568,4578,4678,5678
如果考虑排列顺序,则有70*4!=70*4*3*2*1=1680组
（1234,1243,1324,1342,1423,1432,---------）