Validating primes with regular expressions

Today we see this quite wonderful verification method, the original code is JS, but the algorithm for Py also applies.

The original code is as follows:

1 functionSS (d) {2     if(d <= 3) {3         return true;4     }5     //turn the value into 1116     varstr = ";7      while(--d >= 0) {8str + = 1;9     }TenConsole.log ("str:", str); One     return!/^ (11+?) \1+$/. Test (str) A } -  - //Test the  for(vari = 2; I < 100; i++) { -     if(SS (i)) { - Console.log (i) -     } +}

The experimental results show that the algorithm is effective indeed.

The algorithm actually refers to a string with a length equal to 1 for the number conversion, and then matches the string.

In non-greedy mode, the 11+ can match 11, or it can match to 111, and then by \1 the reverse reference, you can match both modes. These two modes are judged to be non-prime (the result of the regular test method is not), and the prime number is not satisfied.

The specific mathematical principles are not well understood at the moment and are recorded for additions.

The advantage of this algorithm is that it is not necessary to traverse the N/2 sequence sequentially, and it is very effective in the case of limited computational capacity. However, due to the need to build a string of numeric size length, if the value is too large, it consumes considerable memory and can cause memory overflow. Can be thought of as a solution for space-changing time.

Validating primes with regular expressions