Primes whose first and last number is 3: Difference between revisions
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2251 under 1000000 |
2251 under 1000000 |
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</pre> |
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=={{header|Phix}}== |
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Works for any digit, partly inspired by the Wren entry. |
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<!--<lang Phix>(phixonline)--> |
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<span style="color: #008080;">function</span> <span style="color: #000000;">primes_with_first_and_last_digit</span><span style="color: #0000FF;">(</span><span style="color: #004080;">integer</span> <span style="color: #000000;">d</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">p10</span><span style="color: #0000FF;">)</span> |
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<span style="color: #000080;font-style:italic;">-- d should be 0..9 |
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-- p10 should be 1 for 10, 4 for 10,000, 6 for 1,000,000, etc</span> |
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<span style="color: #008080;">if</span> <span style="color: #000000;">d</span><span style="color: #0000FF;"><</span><span style="color: #000000;">0</span> <span style="color: #008080;">or</span> <span style="color: #000000;">d</span><span style="color: #0000FF;">></span><span style="color: #000000;">9</span> <span style="color: #008080;">then</span> <span style="color: #7060A8;">crash</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"d is not a digit!"</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span> |
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<span style="color: #008080;">if</span> <span style="color: #000000;">d</span><span style="color: #0000FF;">=</span><span style="color: #000000;">2</span> <span style="color: #008080;">or</span> <span style="color: #000000;">d</span><span style="color: #0000FF;">=</span><span style="color: #000000;">5</span> <span style="color: #008080;">then</span> <span style="color: #008080;">return</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">d</span><span style="color: #0000FF;">}</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span> |
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<span style="color: #008080;">if</span> <span style="color: #7060A8;">even</span><span style="color: #0000FF;">(</span><span style="color: #000000;">d</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">then</span> <span style="color: #008080;">return</span> <span style="color: #0000FF;">{}</span> <span style="color: #008080;">end</span> <span style="color: #008080;">if</span> |
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<span style="color: #004080;">sequence</span> <span style="color: #000000;">res</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">filter</span><span style="color: #0000FF;">({</span><span style="color: #000000;">d</span><span style="color: #0000FF;">},</span><span style="color: #7060A8;">is_prime</span><span style="color: #0000FF;">)</span> |
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<span style="color: #008080;">for</span> <span style="color: #000000;">i</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #000000;">p10</span><span style="color: #0000FF;">-</span><span style="color: #000000;">1</span> <span style="color: #008080;">do</span> |
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<span style="color: #004080;">integer</span> <span style="color: #000000;">p</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">power</span><span style="color: #0000FF;">(</span><span style="color: #000000;">10</span><span style="color: #0000FF;">,</span><span style="color: #000000;">i</span><span style="color: #0000FF;">)</span> |
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<span style="color: #008080;">for</span> <span style="color: #000000;">candidate</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">d</span><span style="color: #0000FF;">*</span><span style="color: #000000;">p</span><span style="color: #0000FF;">+</span><span style="color: #000000;">d</span> <span style="color: #008080;">to</span> <span style="color: #0000FF;">(</span><span style="color: #000000;">d</span><span style="color: #0000FF;">+</span><span style="color: #000000;">1</span><span style="color: #0000FF;">)*</span><span style="color: #000000;">p</span><span style="color: #0000FF;">-</span><span style="color: #000000;">1</span> <span style="color: #008080;">by</span> <span style="color: #000000;">10</span> <span style="color: #008080;">do</span> |
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<span style="color: #008080;">if</span> <span style="color: #7060A8;">is_prime</span><span style="color: #0000FF;">(</span><span style="color: #000000;">candidate</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">then</span> |
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<span style="color: #000000;">res</span> <span style="color: #0000FF;">&=</span> <span style="color: #000000;">candidate</span> |
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<span style="color: #008080;">end</span> <span style="color: #008080;">if</span> |
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<span style="color: #008080;">end</span> <span style="color: #008080;">for</span> |
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<span style="color: #008080;">end</span> <span style="color: #008080;">for</span> |
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<span style="color: #008080;">return</span> <span style="color: #000000;">res</span> |
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<span style="color: #008080;">end</span> <span style="color: #008080;">function</span> |
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<span style="color: #004080;">sequence</span> <span style="color: #000000;">res</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">primes_with_first_and_last_digit</span><span style="color: #0000FF;">(</span><span style="color: #000000;">3</span><span style="color: #0000FF;">,</span><span style="color: #000000;">4</span><span style="color: #0000FF;">)</span> |
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<span style="color: #004080;">string</span> <span style="color: #000000;">sres</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">join_by</span><span style="color: #0000FF;">(</span><span style="color: #7060A8;">apply</span><span style="color: #0000FF;">(</span><span style="color: #004600;">true</span><span style="color: #0000FF;">,</span><span style="color: #7060A8;">sprintf</span><span style="color: #0000FF;">,{{</span><span style="color: #008000;">"%5d"</span><span style="color: #0000FF;">},</span><span style="color: #000000;">res</span><span style="color: #0000FF;">}),</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #000000;">10</span><span style="color: #0000FF;">)</span> |
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<span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"There are %d primes under 10,000 which begin and end in 3:\n%s\n"</span><span style="color: #0000FF;">,{</span><span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">res</span><span style="color: #0000FF;">),</span><span style="color: #000000;">sres</span><span style="color: #0000FF;">})</span> |
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<span style="color: #000000;">res</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">primes_with_first_and_last_digit</span><span style="color: #0000FF;">(</span><span style="color: #000000;">3</span><span style="color: #0000FF;">,</span><span style="color: #000000;">6</span><span style="color: #0000FF;">)</span> |
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<span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"There are %d primes under 1,000,000 which begin and end in 3\n"</span><span style="color: #0000FF;">,{</span><span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">res</span><span style="color: #0000FF;">)})</span> |
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<!--</lang>--> |
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{{out}} |
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<pre> |
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There are 33 primes under 10,000 which begin and end in 3: |
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3 313 353 373 383 3023 3083 3163 3203 3253 |
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3313 3323 3343 3373 3413 3433 3463 3533 3583 3593 |
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3613 3623 3643 3673 3733 3793 3803 3823 3833 3853 |
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3863 3923 3943 |
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There are 2251 primes under 1,000,000 which begin and end in 3 |
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</pre> |
</pre> |
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