combination-and-permutation v1.0.2

Combination and Permutation computation 组合和排列计算

1. Combination 组合

Every combination has same probability.
每一种组合都有相同的概率。

execute combination(3) 10000 times, we got:
执行了10000次combination(3)，结果如下：
'2,3' => 1469,
'1,2' => 1370,
'1,2,3' => 1447,
'3' => 1400,
'1,3' => 1413,
'1' => 1471,
'2' => 1430

2. Permutation 排列

Obviously, permutations and combinations are different, and permutations with different numbers have different probabilities。
很明显，排列跟组合不同，不同数量数字的排列具有不同的概率。

execute permutation(3) 10000 times, we got:
执行了10000次permutation(3)，结果如下：
'3' => 1417,
'2,1,3' => 264,
'2,3' => 671,
'3,1,2' => 267,
'3,1' => 708,
'1,3' => 698,
'2' => 1412,
'2,3,1' => 230,
'3,2,1' => 226,
'1,2,3' => 260,
'3,2' => 746,
'1,2' => 750,
'1,3,2' => 225,
'1' => 1414,
'2,1' => 727