wanghan519

awk写了个幂集，不知道对不对，可以存入文件a.awk再运行echo asdfg | awk -f a.awk试一下
只考虑了组合，没考虑排列。。。

function powerset(x, y) {
    if (length(x) > 3 || y > length($0)) {
        print x
        return
    }
    powerset(x, y + 1)
    powerset(x substr($0, y, 1), y + 1)
}
{
    powerset("", 1)
}
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wanghan519

python最简单，因为有itertools，

import itertools
s = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'
with open(r'a.txt','w') as f:
    for i in range(1, 5):
        for j in itertools.permutations(s, i):
            f.write(''.join(j)+'\n')
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前两天刚提过的nushell可以方便的写sql，似乎sql写递归也很方便

with recursive c as (
select x, 1 n from t
union all
select c.x || t.x, c.n + 1
from c join t
where c.n < 4 and c.x not like '%' || t.x || '%'
)
select x from c;
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或者就像上面那样再试试awk递归怎么写，上面那是列出所有组合，没考虑全排列