Largest difference between adjacent primes: Difference between revisions
Largest difference between adjacent primes (view source)
Revision as of 17:50, 3 June 2023
, 11 months agoCreated Nim solution.
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(Created Nim solution.) |
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{{out}}<pre>
114
</pre>
=={{header|Nim}}==
<syntaxhighlight lang="Nim">import std/[bitops, math]
type Sieve = object
data: seq[byte]
func `[]`(sieve: Sieve; idx: Positive): bool =
## Return value of element at index "idx".
let idx = idx shr 1
let iByte = idx shr 3
let iBit = idx and 7
result = sieve.data[iByte].testBit(iBit)
func `[]=`(sieve: var Sieve; idx: Positive; val: bool) =
## Set value of element at index "idx".
let idx = idx shr 1
let iByte = idx shr 3
let iBit = idx and 7
if val: sieve.data[iByte].setBit(iBit)
else: sieve.data[iByte].clearBit(iBit)
func newSieve(lim: Positive): Sieve =
## Create a sieve with given maximal index.
result.data = newSeq[byte]((lim + 16) shr 4)
func initPrimes(lim: Positive): seq[Natural] =
## Initialize the list of primes from 2 to "lim".
var composite = newSieve(lim)
composite[1] = true
for n in countup(3, sqrt(lim.toFloat).int, 2):
if not composite[n]:
for k in countup(n * n, lim, 2 * n):
composite[k] = true
result.add 2
for n in countup(3, lim, 2):
if not composite[n]:
result.add n
let primes = initPrimes(1_000_000)
var prev = 0
var largestDiff = 0
for n in primes:
largestDiff = max(largestDiff, n - prev)
prev = n
echo "Largest difference: ", largestDiff
</syntaxhighlight>
{{out}}
<pre>Largest difference: 114
</pre>
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