5kyu_PrimesInNumbers.js

// 5kyu - Primes in Numbers

// Given a positive number n > 1 find the prime factor decomposition of n. The result will be a string with the following form :

//  "(p1**n1)(p2**n2)...(pk**nk)"
// with the p(i) in increasing order and n(i) empty if n(i) is 1.

// Example: n = 86240 should return "(2**5)(5)(7**2)(11)"

function primeFactors(n){
  for (var i=2, res="", f; i <= n; i++) {
    f=0;
    while (n%i == 0) { f++; n/=i }
      res += f ? "(" + ( f>1 ? i+"**"+f  : i ) +")" : "";
  }
  return res || "("+n+")";
}