primes

问题 OK, my understanding of the mathematical workings of RSA may not be as deep as it should, so feel free to slap me over the head if this is stupid: To generate a private key, we need two random big primes. There is no algorithm that can do that precisely and efficiently, but there are algorithms that can generate big numbers that have a 99.99999...(a bazillion 9s)...999% probability of being prime. My question is: what happens if, by a phenomenal stroke of bad luck, when you were generating

问题 How would one implement a list of prime numbers in Haskell so that they could be retrieved lazily? I am new to Haskell, and would like to learn about practical uses of the lazy evaluation functionality. 回答1: Here's a short Haskell function that enumerates primes from Literate Programs: primes :: [Integer] primes = sieve (2 : [3, 5..]) where sieve (p:xs) = p : sieve [x|x <- xs, x `mod` p > 0] Apparently, this is not the Sieve of Eratosthenes (thanks, Landei). I think it's still an instructive

问题 I have to determine if all the numbers in a list are prime numbers and then return a boolean "True" or "False" statement depending on the outcome. I made some conditional statements inside of a for loop to see if the number was prime or not. Here's the code: def all_primes(xs): is_prime = None for i in xs: if i < 2: is_prime = False return is_prime break elif (i % 2 == 0) and (i % i == 1): is_prime = False return is_prime break else: is_prime = True return is_prime The problem is, and I saw

问题 I need to find the highest prime number in a given range. Here is my code which works for 0-100 but if I give 0-125 it is showing prime number as 125. <?php $flag=0; $b=125; for($i=$b;$i>=0;$i--) { if($i%2!=0) { for($b=3;$b<10;$b++) { if($flag==0) { echo('<br>'); if($i%$b!=0) { echo('highest prime number is'.$i); $flag=1; break; } elseif ($i%$b==0) { break; } } } } } ?> In the above code I have taken the range from 0-125 回答1: Yup the problem is algorithmic... 1) You'll need to check up till

问题 I'd like to print out all prime numbers from an array with method. I can do it with one int but don't know how to return certain numbers from array. Thanks for help! public static boolean isPrime(int [] tab) { boolean prime = true; for (int i = 3; i <= Math.sqrt(tab[i]); i += 2) if (tab[i] % i == 0) { prime = false; break; } for(int i=0; i<tab.length; i++) if (( tab[i]%2 !=0 && prime && tab[i] > 2) || tab[i] == 2) { return true; } else { return false; } //return prime; } thanks both of you.

问题 By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13. What is the 10 001st prime number? My solution: public class Prime_Number { public static boolean isPrime(long n) { if ((n > 2 && n % 2 == 0) || (n > 3 && n % 3 == 0) || (n > 5 && n % 5 == 0) || n == 0 || n == 1) { return false; } return true; } public static void main(String[] args) { int count = 0; int prime = 0; while (prime <= 10001) { if (isPrime(count) == true) { prime++; if (prime ==

问题 This question already has answers here : Program that checks if a number is prime number (5 answers) Closed 11 months ago . def is_prime(x): if x < 2: return False else: for n in range(2, x): if x % n == 0: return False else: return True print is_prime(9) returns True instead of False . I don't quite understand. The range (2,9) includes this list: 2,3,4,5,6,7,8 and 9 % 3 == 0 , So how come I do not get False as the answer of that function? 回答1: This is because you don't actually loop, as you

问题 I want to write a function in R which accepts a list of integers and returns only the values which are prime. So far I have this: primefindlist<-function(n){ return(n[n==2 | all(n %% seq(2,ceiling(sqrt(n)),by=1) !=0)]) } But I keep getting an error message when I run the function e.g; primefindlist(c(7,11)) Error in seq.default(2, ceiling(sqrt(n)), by = 1) : 'to' must be of length 1 Anyone got any ideas how to overcome this? Also the code below tells me if a single integer is prime or not ie

问题 I have a data.frame that has 131 columns. I need to part this into groups of about 10 to 15 variables (i.e., splitting by column, not by row!). Obviously, as 131 is a prime number, not all the new dataframes can be of equal length... I searched for an answer in the posts How to cut data in even pieces in R? Split a vector into chunks in R Splitting a large vector into intervals in R But they all seem to assume that the new data frames are of equal size. EDIT thanks to the comments below, I

问题 I am trying to check if a number is prime using recursion. I was required to use a recursive helper function, but I am not sure how I should implement it. I think I know the algorithm, but I've never tried to use a recursive helper function in Racket. This is my current thoughts: See if n is divisible by i = 2 Set i = i + 1 If i^2 <= n continue. If no values of i evenly divided n , then it must be prime. This is what I have so far... (define (is_prime n) (if (<= n 1) #f (if (= (modulo n 2) 0)