A colleague of mine once posted a hiring question to ask prospective developers: “What is the least significant 10 digits of the series: .. ?”

The trick of course is to recognize that it’s solved with modular exponentiation. He presented a page of java code which was akin to what he was looking for. I did a one-liner on the bash command line and flunked the test. (He was looking for java programmers.)

My one liner:

$ for i in {1..1000} ; do echo "$i $i 10000000000|p" | dc ; done | awk '{t=($1+t)%1e10} END {print t}' 9110846700

I like my recursive awk solution better however, as it was more fun..

$ echo 1000 | awk ' > function powermod(n,p) { > if (p == 1) return n > else return n*powermod(n,p-1) % 1e10 > } > function add(n) { > if (n == 1) return 1 > return (add(n-1) + powermod(n,n)) % 1e10 > } > > NF { print add($1) % 1e10 } > ' 9110846700

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**How would you solve it in your favourite language?**