Pandigital prime
- Task
The following problem is taken from Project Euler.
We shall say that an n-digit number is pandigital if it makes use of all the digits 1 to n exactly once. For example, 2143 is a 4-digit pandigital and is also prime.
What is the largest n-digit pandigital prime that exists?
Assume that the problem is talking about decimal numbers.
Ring
<lang ring> load "stdlib.ring" see "working..." + nl see "The largest pandigital prime is:" + nl
limit = 9876543
for n = limit to 2 step -2
flag = 1 strn = string(n) if isprime(n) for m = 1 to len(strn) ind = count(strn,strn[m]) if ind != 1 flag = 0 ok next if flag = 1 pand = n exit ok ok
next
see "" + pand + nl
see "done..." + nl
func count(cString,dString)
sum = 0 while substr(cString,dString) > 0 sum++ cString = substr(cString,substr(cString,dString)+len(string(sum))) end return sum
</lang>
- Output:
The largest pandigital prime is: 9,876,413
Wren
<lang ecmascript>import "/math" for Int import "/fmt" for Fmt
// generates all permutations in lexicographical order var permutations = Fn.new { |input|
var perms = [input] var a = input.toList var n = a.count - 1 for (c in 1...Int.factorial(n+1)) { var i = n - 1 var j = n while (a[i] > a[i+1]) i = i - 1 while (a[j] < a[i]) j = j - 1 var t = a[i] a[i] = a[j] a[j] = t j = n i = i + 1 while (i < j) { t = a[i] a[i] = a[j] a[j] = t i = i + 1 j = j - 1 } perms.add(a.toList) } return perms
}
System.print("The largest pandigital decimal prime which uses all the digits 1..n once is:") for (n in 9..1) {
var perms = permutations.call((1..n).toList) for (i in perms.count - 1..0) { if (perms[i][-1] % 2 == 0 || perms[i][-1] == 5) continue var p = Num.fromString(perms[i].join()) if (Int.isPrime(p)) { Fmt.print("$,d", p) return } }
}</lang>
- Output:
The largest pandigital decimal prime which uses all the digits 1..n once is: 7,652,413