primes (prime number)
Also known as Prime number, refers to the number of natural numbers greater than 1 , except 1 and the number itself, can not be divisible by other natural numbers (can also be defined as only 1 and the number itself two factors of the number).
Algorithm principle
A simple but slow method of verifying whether a number n is a prime is a trial division. This method tests whether n is a multiple of an integer between 2 and any .
Implementation example (Java language)
1 Public classPrimenumberexample {2 3 Public Static BooleanIsPrime (LongN) {4 5 if(N > 2 && (n & 1) = = 0)6 return false;7 /*Use Trial Division:8 * 1. Only odd numbers need to be tested9 * 2. Test range from 2 to square root {n}, and vice versa*/Ten for(inti = 3; I * I <= N; i + = 2) One if(n% i = = 0) A return false; - return true; - } the - Public Static voidMain (string[] args) { - intWhich=0; - for(inti=2;i<=1000;i++){ + if(IsPrime (i)) { -which++; + if(which% 10 = = 0) {System.out.println ();} ASystem.out.print (i+ ","); at } - } - System.out.println (); -System.out.print ("Total" +which+ "prime number.")); - } - in}
Results
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, 101, 103, 107, 109,
113, 127, 131, 137, 139, 149, 151, 157, 163, 167,
173, 179, 181, 191, 193, 197, 199, 211, 223, 227,
229, 233, 239, 241, 251, 257, 263, 269, 271, 277,
281, 283, 293, 307, 311, 313, 317, 331, 337, 347,
349, 353, 359, 367, 373, 379, 383, 389, 397, 401,
409, 419, 421, 431, 433, 439, 443, 449, 457, 461,
463, 467, 479, 487, 491, 499, 503, 509, 521, 523,
541, 547, 557, 563, 569, 571, 577, 587, 593, 599,
601, 607, 613, 617, 619, 631, 641, 643, 647, 653,
659, 661, 673, 677, 683, 691, 701, 709, 719, 727,
733, 739, 743, 751, 757, 761, 769, 773, 787, 797,
809, 811, 821, 823, 827, 829, 839, 853, 857, 859,
863, 877, 881, 883, 887, 907, 911, 919, 929, 937,
941, 947, 953, 967, 971, 977, 983, 991, 997,
A total of 168 prime numbers.
Reference Links:
Prime number-Wikipedia: https://zh.wikipedia.org/wiki/%E7%B4%A0%E6%95%B0
Very Simple Prime number test:http://stackoverflow.com/questions/14650360/ Very-simple-prime-number-test-i-think-im-not-understanding-the-for-loop
Algorithm for prime number (Java language)