小学奥数题
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| Language | Raku |
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| Owner | seaker |
| Created | 3 years ago |
| Modified | 3 years ago |
| Visibility | Public |
# 若一个四位数，它的任意两位数字之差均等于它的某个数字，且每个数字都能作为差被取到。例如2022。而1234则不符合。问这样的数有多少个？
my $cnt = 0;
for 1000..9999 -> \n {
my @a = n.comb.sort;
if @a.combinations(2).map({ .[1] - .[0] }).sort.unique.join eq @a.unique.join {
put n;
++$cnt;
}
}
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