like 17, is a prime, when reversed, 71 is also a prime.
We manage to arrive at this code but we cant finish it.
#include <stdio.h>
main()
{
int i = 10, ...
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What is the shortest C code to "Calculate the n-th prime"?
Shortest in terms of significant characters, i.e. the number of semicolons, non-whitespace characters, keywords and commas.
Input:
Integers n from the standard input, ... |
I've been doing a few of the challenges on the Sphere Online Judge (SPOJ), but I can't seem to get the second problem (the prime generator) to ... |
I'm a third year irregular CS student and ,i just realized that i have to start coding.
I passed my coding classes with lower bound grades so that i haven't a ... |
So what I am trying to is find all the prime factors of a number n. When I give it 126 it gives me 2, 3, and 7 but when I ... |
I saw this c code of using Sieve method of Eratosthenes to find primes, but I cannot extend it to even larger integers (for example, to 1000000000 and even ... |
Possible Duplicate:
Fastest primality test
Can somebody give an efficient algorithm for determining primality of an number?
The conventional iteration method seems to take an lots ... |
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In your for loop instead of the end condition being a test against x, the current number you are checking, you need to use a separate variable to keep a count of the number of primes you have found and test against that instead. Also your loop at line 13 works but has a lot of scope for optimisation. |
P: n/a jzakiya This is to announce the release of my paper "Ultimate Prime Sieve -- Sieve of Zakiiya (SoZ)" in which I show and explain the development of a class of Number Theory Sieves to generate prime numbers. I used Ruby 1.9.0-1 as my development environment on a P4 2.8 Ghz laptop. You can get the pdf of my paper ... |
Hi, I missed a couple classes due to being sick this past week and I am having trouble getting steered in the right direction for my programming assignment. I'd ask the professor for help but he has a total of four hours during the week for office hours, all of which I have a class. But anyways... Write a C program ... |
/*I can program it if user gives an upper limit. If user wants to generate first n twin primes, I'm failing to do that. Slight modifications are required. Thnaks.*/ // TWIN PRIMES BELOW A RANGE #include #include int main(void) { long r,i,j,k=1,a[1000],num=0; printf("Enter Upper Limit: "); scanf("%ld",&r); for(i=3;i<=r;++i) { int flag=0; for(j=2;j<=sqrt(i)+1;++j) if(i%j==0) {flag=1;break;} if(flag==0) {a[k]=i;k++;} } printf( "\nTwin ... |
"ume$h" //FIRST n PRIMES #include #include > int main(void) { long int i,j=3,count=1; int n,flag=0; cout<<"How many primes?"; cin>>n; cout<<"2, "; while(count3 && flag==0) {cout< |
theorem states that: Integer n is prime if and only if (x +1)^n x^n +1 (mod n) in Z[x]. so I testing it, but values doesn't match ... and I don't se why.. I guess :) it's some thing wrong in my implementation... hope you can help out :) #include #include void id_prime(int i); int power (int base, ... |
makes sense! thanks....only problem is i dont think i am allowed to use arrays yet Then you can create the tmp, and store it, and then calculate the next one. At that point, you check the tmp to the current (in the 'if (n==prime)' loop), and then output or whatever. The tricky part will be the initialization - you start from ... |
lovecreatesbea...@gmail.com Hello experts, The following is_prime function doesn't call a library function and it works. Does it have bugs like "integer overflow": int factor; factor * factor, or it's not single entry/exit, or others... Thank you. /*return 0 if num is a prime number otherwise 1*/ bool is_prime(int num) { int factor; if (num < 2) return 1; for (factor = ... |
Hello all, Is there a function in the standard C library which returns a prime number which is also pseudo-random? Assuming there isn't, as it appears from the docs that I have, is there a better way than to fill an array of range 0... RAND_MAX with pre-computed primes and using the output of rand() to index into it to extract ... |
Hello, I'm taking an independant course in C++, and one of my questions asks to use the following algorithm to deturmine the factors of any given number: -- Initialize a counter at 2 So Long as long as the counter is less than or equal to the number if the counter divides the number evenly display the counter divide the number ... |
Hi all, I'm currently working on a Project Euler challenge calling for me to find the largest prime factor of a given number. I have a working code written (I know it works, as I've tested it with smaller numbers). However, when calculating the large number (600 billion) that PE gives me, it is taking an extremely long time. Project Euler ... |
int isPrime(int n) { int k; if (n < 2) { return 0; } for (k=2; k > n; k++) { if ((n % k)==0) return 0; } return 1; } /* Implement your findPrime function here. */ int findPrime(int n) { int nn; int p; p = n * 2; /* Maximum range of finding a prime number */ for(nn=n+1; ... |
Morning, I bought the book, "Learn C on the Mac" So far have been enjoying it but have become stumped at one section. I was hoping someone could help. Its to do with the exercise on prime numbers in chap 6. Regarding the loop to determine whether a number is prime - to me it sounds like the program is able ... |
22. Prime digits cboard.cprogramming.comI am doing multiplication of numbers such that every digits is a prime, i don,t know what it the problem ....when i run my program ,i don,t get all prime...i don,t know where the problem is from.please help me tell me what i did wrong. Code: #include #include #include #include bool check_prime(int); int main(){ int flag=0; int ... |
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Heres my problem. I completed a sieve originally that did not include sqrt or dividing just by odd numbers other then 2. But when I used it, it was too slow for the really big numbers so, I was told that in order to fix it the best thing to do was to just use the sqrt of the the original ... |
Largest prime factor... I am trying to solve some problems on Project Euler, and currently have very little experience with or knowledge about programming. I've learned up until while loops :P Anyways, I decided to see how many I can do before I have to move on and continue learning. This problem was the one I decided to stop after, as ... |
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Hi folks, I'm trying to implement the Miller Rabin Prime Test into C as an exercise and I was hoping you could give me a few pointers where to look for my mistake. The following Code should work if i understood the Algorithm correctly, but it sometimes(pretty often really) tags primes as nonprimes(or did the rules change and 17 isn't a ... |
An odd number is not a prime number if it has a number of at least 3 and less than or equal to the square root of the number that divides it. Since it's odd, 2 doesn't divide it, so per definition of a prime number an odd number that is not prime has a divisor from 3 to the square ... |
29. prime no cboard.cprogramming.com |
Hello everyone, My Background: I am a novice C programmer. I simply bought a book* and am trying to teach my self out of general interest in computer science. My Trouble: As an exercise, I tried to write a program that would give the user the n'th prime number when given n. I thought I had worked out all the kinks ... |
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Do you mean having 60 as the input and "2, 2, 3, 5" as the output, reducing a number to prime factors? This shouldn't be too difficult. Start with 2, the lowest possible prime number. If "Input % 2 == 0", then factor 2 out of it. Write the output and divide by 2. If the number still is a multiple ... |
33. Prime cboard.cprogramming.com |
34. Prime factor cboard.cprogramming.com |
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Hi you all! This is my very first post in the forum :P I'm sorry for my english, that's because I'm from Portugal. Anyway, I have this work assignment I need to do for school but was in need of your help with the last part of it. As in the tittle, I need a function that factorizes a given number ... |
/* find primes */ #include #include int check_prime( int number ){ int divisor, tf = 1; for( divisor = 2; divisor < number / 2; divisor++ ){ if( number % divisor == 0 ){ tf = 0; break; } } if( tf == 1 ){ printf("%i ",number); } } int main(int argc, char *argv[]){ int number; for( number = ... |
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Code: #include //declaracion de variables. int m, n, I, num; void LeerDatos() { printf("Ingrese el Primer Numero: "); scanf("%d",&m); printf("Ingrese el Segundo Numero: "); scanf("%d",&n); } void ejecutar() { for (num = m; num <= n; num++) //el contador num va de m a n { for(I = 1; I <= num; I++)//se utiliza la variable I como contador para dividir ... |
Okay i got this primes program working. I have the three files working together to give me a program that is suppose to print how many primes i ask for. THe problem i am having it never stops printing to the screen. If i say 2 to 3000.... it doesnt matter program just prints and prints to screen. I know the ... |
42. prime program cboard.cprogramming.comI am working on quite a few exersizes in a book for a class I am taking and unfortunately, I don't think the book is any good. Every example they give has errors that you have to figure out and it has made learning this diffucult. I am currently working a few programs, one of them dealing with primes. its purpose ... |
#include #include #define MAX 100 #define TRUE (1 == 1) #define FALSE (1 == 0) int main(int argc, char *argv[]){ int p [MAX]; int i, n, candidat; int divisible; p[0]=2; p[1]=3; n=2; candidat = p[n-1] + 2; while (n < MAX) { divisible = FALSE; for (i = 0; (i < n) && !divisible; i++) divisible = ((candidat % ... |
i found a set of beginner's problems to solve...i came up with a solution to this one: print out all the prime pairs (prime numbers that differ only by 2) from 3 - 10,000. Code: #include #include main(){ int this_number, divisor, not_prime; int array[1500]; int position = 0; this_number = 3; while(this_number < 10000){ divisor = this_number / 2; ... |
45. Prime factor cboard.cprogramming.comCode: /* divisors.c -- nested ifs display divisors of a number */ #include #include #define NO 0 #define YES 1 int main(void) { long num, div; int prime; /*potential divisors */ printf("Please enter an integer for analysis; "); printf("Enter q to quit.\n"); while (scanf("ld", &num) == 1) { for (div = 2, prime = YES; (div * div) <= ... |
Code: /* Ryan Perrott CMSC 104 0201 Lab 7 11/21/02 Due: 11/24/02 Description: This program uses a function to determine if the number is prime and then prints out all the prime numbers between 1-10000. */ #include #include int prime( int ); /* function prototype */ int main() { int x; for(x=1; x<=10000; x++;) { if( prime( x ) ... |
#include #include #include"simpio.h" #include"genlib.h" #define LowerLimit 2 #define UpperLimit 100 #define TRUE 1 #define FALSE 0 bool isPrime (int num); main() { int num; printf("The prime numbers in the range of 1-100 are:\n\n"); for (num=LowerLimit; num<=UpperLimit; num++) if (isPrime (num) == 1) printf("%d\n",num); } bool isPrime (int num) { int j; for (j=2; j<=sqrt(num); j++) { if (num%j==0) return 1; else ... |
48. prime no's cboard.cprogramming.com#include #define TABLE_SIZE(table) sizeof(table) / sizeof(table[0]) static const int prime_table[] = { /* Empty element */0, 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, }; int main ( void ) { int index; puts ( "Prime numbers from 2 to 100:" ); for ... |
49. prime # query cboard.cprogramming.comCode: #include #include #define TRUE 1; #define FALSE 0; void getNumber(int *number); int isPrime(int number); int main() { int number; getNumber(&number); if (isPrime(number)) printf("\n%d is a prime number\n", number); else printf("\n%d is not a prime number\n", number); return 0; } void getNumber(int *number) { printf("Please enter a positive number "); if (scanf("%d", number) != 1) { printf("Invalid number entered\n"); ... |
While the above posters are correct, this is something you should research on your own, I will recognize that using even Google will yield difficulties in finding what you're looking for... See, here is the difference between computer PROGRAMMING and computer SCIENCE. Programming means just writing the program and using some algorithm that either you come up with yourself, or you ... |
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52. Primes.c help cboard.cprogramming.comCode: /* primes.cpp * * This program calculates the primes numbers b/w 2 and 10,000 * Meghavi Shah * November 4, 2001 * CS133U, Lab 4 */ #include bool isPrime (int); int main () { int number; for (number = 2; number < 10000; number++) if (isPrime(number) == 1) printf("%d",number); return 0; } /* end function main */ /********************************************************************** * ... |
Search for factors and if you find it keep dividing by it till the number is no longer divisble by it, after you are done with 2 you can start with 3 increment by 2 as all the other factors will be odd also note 0 and 1 are neither composite nor prime , the program below is slightly longer then ... |
Hi everyone, I'm taking my first C class this semester, and I'm kind of stuck on this assignment. We need to: 1) Ask the user for two positive integers 2) Compute and print out the largest common prime factor Ok, so my problem is that the code doesn't always work correctly. For example, if I use the numbers 5 and 15, ... |
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#include #include int main () { int flag=1,B=1024,n=1,count=3,flag1; struct primes { int no; struct primes * next; }; typedef struct primes PrimesList; PrimesList *list,*temp, *initial; list=(PrimesList*)malloc(sizeof(PrimesList)); temp=list; temp->no=2; temp->next=(PrimesList*)malloc(sizeof(PrimesList)); temp=temp->next; temp->next=NULL; temp->no=3; temp->next=(PrimesList*)malloc(sizeof(PrimesList)); temp=temp->next; temp->next=NULL; temp->no=5; temp->next=(PrimesList*)malloc(sizeof(PrimesList)); temp=temp->next; temp->next=NULL; int start=7; int i=start; while (i<=B) { initial=list; flag1=0; while ( ((initial->next)!= NULL) && (flag1==0) ) { if ((i% initial->no)==0) ... |
well the project is find the largest prime factor of a number (any number between 1 and 100.000.000) and compare it with a number B(lets say 1024). i am about to build a list of primes up to 1024.. then i 've got two ideas.. the one -brute force divisibility testings..start from the firti prime and proceed to the next one ... |
I am new to c and have the following problem: I have this code I need to modify to find happy prime numbers. (A happy number is defined by the following process. Starting with any positive integer, replace the number by the sum of the squares of each of its digits, and repeat the process until the number equals 1 (where ... |
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Your while loop should either be removed or be expanded to include the user input above it. It is meaningless otherwise. Your for loop does the wrong thing. Look at the code you wrote and explain it yourself in plain English. You take each number between 2 and the chosen number. You see if it divides with no remainder. If there ... |
Hi im new here and i did a search to try to find anything related but couldnt find anything... im new to c, i know some web programing like html and php. I need to create a program that you can imput 2 numbers and it gives back the highest prime number by which you can divide the number... something like ... |
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I modified my code from http://forums.devshed.com/t125318/s.html to make this: Code: #include class BitMap{ unsigned int m_intHowHigh2Go, m_intEntries, m_intBitsPerEntry; unsigned long *m_lptrBitMask; public: BitMap(unsigned int HowHighToLook){ m_intHowHigh2Go = HowHighToLook; m_intBitsPerEntry = sizeof(unsigned long) * 8; m_intEntries = m_intHowHigh2Go / m_intBitsPerEntry; m_intEntries++; m_lptrBitMask = new unsigned long[m_intEntries];; for (unsigned int i=0; i |
#include #include // remove, not needed void main() // main is NEVER void, it's int int N,R; // why aren't you indenting so we can follow this? clrscr(); // Get rid of this annoying line printf("Please enter a no.:\n"); scanf("%d",&N); { for(R==2;R>N;R++) if(N%R==0) printf("%d",R) else if(N%R!=0) printf("%d",N); else printf("Invalid"); } getch(); // Get rid of this, it's not standard. // Use ... |
#include #include int main() { int a,n,prime,l=2; printf("Please enter a positive integer.\n"); printf("To end the program enter a negetive integer.\n"); while(l>1){ scanf("%d",&n); prime=1; if(n<=1) printf("The number is not prime.\n"); else if(n==2) printf("The number is prime.\n"); else{ for(a=2;a<=(int)sqrt(n);a++){ if(!(n%a)) prime=0; } if(prime==0) printf("The number is not prime.\n"); else printf("The number is prime.\n"); } if(n<0){ break; } printf("Please enter a positive integer.\n"); printf("To ... |
#include #include #include void primefactors(int); int pf=0; void main() { int number; int i,j,ct=0; clrscr(); printf("Enter the Number:"); scanf("%d", &number); if(number==2){ printf("Number is Prime and Prime Factor is %d",number); exit(0); } for(i=2;i<=number;i++) { if(number%i==0 && i |
#include #define SIZE 1000001 int main() { int nums[SIZE]; int primes[10000]; int i = 0; int j = 0; for (i = 0; i < SIZE - 1; i++) nums[i] = i; nums[1] = 0; for (i = 4; i <= SIZE - 1; i += 2) nums[i] = 0; for (i = 3; i < SIZE - 1; i ... |
#include /* Find out the prime factors * of a given number and print * them on the screen */ void factorize(int n) { int d = 2; if(n < 2) return; printf("Prime factors of '%d': ", n); /* while the factor being tested * is lower than the number to factorize */ while(d < n) { /* valid prime ... |
#include /* Find out the prime factors * of a given number and print * them on the screen */ void factorize(int n) { int d = 2; if(n < 2) return; printf("Prime factors of '%d': ", n); /* while the factor being tested * is lower than the number to factorize */ while(d < n) { /* valid prime ... |
#include int main() { int maxprimes; int count = 1; int value = 1; int primes[maxprimes]; int composite; int i = 1; int j; printf ("How many primes? "); scanf ("%d", &maxprimes); printf ("2 is prime\n"); primes[0] = 2; while (count < maxprimes){ composite = 0; value += 2; for (j = 1 ; j < maxprimes ; j++) { ... |
/*NOTE: (int)(log(integer number)/log(10)) + 1 = number digits in a number */ #include #include #include bool prime(int); bool circular_prime(int n, int size); int main(void) { int INPUT = 200; int i; int counter = 0; for(i = 2; i < INPUT; i++) if(prime(i) && circular_prime(i, ((log(i)/log(10))+1) ) ) { counter ++; printf("%d \t %d\n", counter, i); //helps show ... |
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#include #include #include /* function to create a random number */ int randomInteger(int low, int high) { static short firstRun = 1; int offset; if(firstRun) { //If this is the first call to this procedure, randomize the seed srand(time(NULL)); //and set first run to 0 so we know its been run firstRun = 0; } offset = low; ... |
#include /* Find out the prime factors * of a given number and print * them on the screen */ void factorize(int n) { int d = 2; if(n < 2) return; printf("Prime factors of '%d': ", n); /* while the factor being tested * is lower than the number to factorize */ while(d < n) { /* valid prime ... |
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#include int gcd(int i, int x); int main(int argc, char *argv[]){ int i, x = 351; printf("351 is relatively prime to:\n"); for(i = 1; i < 351; i++){ if( gcd( i, x ) == 1) printf("%d\n", i); } return 0; } int gcd(int i, int x){ if(x % i == 0) return( i ); return( gcd( x % i, x ... |
HWND hwndText = CreateWindow( TEXT("edit"), // The class name required is combobox TEXT("TEXTBOX test"), // Default text. WS_VISIBLE | WS_CHILD | WS_BORDER | WS_HSCROLL | WS_VSCROLL| ES_MULTILINE | ES_AUTOHSCROLL, // the styles 200,200, // the left and top co-ordinates 100,100, // width and height hwnd, // parent window handle (HMENU)13, // the ID of your combobox hThisInstance, // the instance of ... |
#include #include "genlib.h" #include "simpio.h" int main() { int n1, n2, y, x; printf("This program list all the twin primes.\n"); for (y = 3; y <= 98; y += 2) { if (3 % y != 0 && 5 % y != 0 && 7 % y != 0) { y = y; } for (x = 3; x <= ... |
#include main() { static int n=0, number=1; int fibi (int n, int number); printf ("Following are the first 40 Numbers of the Fibonacci Series:\n"); printf ("1 "); fib (n,number); } fib (int n, int number) { static int i=1; int fibo; if (i==40) { printf ("\ndone"); } else { fibo=n+number; n=number; number=fibo; printf ("\n%d", fibo); i++; fib (n,number); } } |
#include #include int main() /* main program starts here*/ { /*initialize variables for sieve algorithm*/ short int A[SHRT_MAX+1]= {0}; short int prime [5000]; int n, j; int prime_count = 1; int cur_prime = 2; printf ("You want prime numbers up to: "); scanf("%d", &n); while (cur_prime <= SHRT_MAX && prime_count < n) { for (j=2 ; j*cur_prime < SHRT_MAX ... |
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hello everyone,i need to calculate random prime numbers, having at least 230 digits of length, with no noticable delay. Is it possible to do on-the-fly? I was thinking of a list having some hundreds of them which i would use and pick randomly one. Does anybody know of such a list? I will use it to implement rsa encryption.Thanks |