DWITE Online Computer Programming Contest
February 2006

Problem 5

Prime Palindromes

The number 181 is a prime palindrome because it is both a prime number and a palindrome. A palindrome is a number that is the same when read forward as backward. Write a program that determines how many prime palindromes there are between two numbers.

The input will contain five sets of data. Each set will contain two integers, L and U, the range of numbers to determine the prime palindromes. 2 ≤ L ≤ U ≤ 999,999.

The output will contain the number of prime palindromes between L and U, inclusive.

Sample Input (3 sets of data only)

2 10
100 200
10000 20000

Sample Output

4
5
26

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Best Solutions

Point Value: 10
Time Limit: 1.00s
Memory Limit: 16M
Added: Nov 13, 2008

Languages Allowed:
C++03, PAS, C, HASK, ASM, RUBY, PYTH2, JAVA, PHP, SCM, CAML, PERL, C#, C++11, PYTH3

Comments (Search)

Would someone care to enlighten me on where my problem is messed up? Thanks :)

Your check_prime function is too slow. You need a different algorithm. Try reading up on this. http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes

Thanks I will read up on that