Primes whose reversed number is also prime: Difference between revisions
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{{Draft task}} |
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;Task:Find and show here in base ten primes whose reversed number is also prime, where '''n < 1,000''' |
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<br><br> |
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=={{header|Ring}}== |
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<lang ring> |
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load "stdlib.ring" |
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see "working..." + nl |
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see "Primes whose reversed number is also prime:" + nl |
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row = 0 |
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for n = 1 to 1000 |
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strn = string(n) |
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strn = rever(strn) |
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strn = number(strn) |
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if isprime(n) and isprime(strn) |
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see "(" + n + "," + strn + ")" + " " |
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row++ |
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if row%5 = 0 |
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see nl |
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ok |
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ok |
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next |
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see nl + "Found " + row + " prime numbers" + nl |
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see "done..." + nl |
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func rever(str) |
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strb = "" |
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for n = len(str) to 1 step -1 |
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strb += str[n] |
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next |
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return strb |
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</lang> |
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{{out}} |
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<pre> |
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working... |
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Primes whose reversed number is also prime: |
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(2,2) (3,3) (5,5) (7,7) (11,11) |
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(13,31) (17,71) (31,13) (37,73) (71,17) |
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(73,37) (79,97) (97,79) (101,101) (107,701) |
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(113,311) (131,131) (149,941) (151,151) (157,751) |
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(167,761) (179,971) (181,181) (191,191) (199,991) |
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(311,113) (313,313) (337,733) (347,743) (353,353) |
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(359,953) (373,373) (383,383) (389,983) (701,107) |
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(709,907) (727,727) (733,337) (739,937) (743,347) |
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(751,157) (757,757) (761,167) (769,967) (787,787) |
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(797,797) (907,709) (919,919) (929,929) (937,739) |
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(941,149) (953,359) (967,769) (971,179) (983,389) |
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(991,199) |
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Found 56 prime numbers |
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done... |
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</pre> |
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