#UT152. [USACO1.5.2]回文质数 Prime Palindromes
[USACO1.5.2]回文质数 Prime Palindromes
Prime Palindromes
The number 151 is a prime palindrome because it is both a prime number and a palindrome (it is the same number when read forward as backward). Write a program that finds all prime palindromes in the range of two supplied numbers a and b (5 <= a < b <= 100,000,000); both a and b are considered to be within the range .
PROGRAM NAME: pprime
INPUT FORMAT
- Line 1: Two integers, a and b
SAMPLE INPUT (file pprime.in)
5 500
OUTPUT FORMAT
The list of palindromic primes in numerical order, one per line.
SAMPLE OUTPUT (file pprime.out)
5
7
11
101
131
151
181
191
313
353
373
383
HINTS
- Generate the palindromes and see if they are prime.
- Generate palindromes by combining digits properly. You might need more than one of the loops like below.
/* generate five digit palindrome: */
for (d1 = 1; d1 <= 9; d1+=2) { /* only odd; evens aren't so prime */
for (d2 = 0; d2 <= 9; d2++) {
for (d3 = 0; d3 <= 9; d3++) {
palindrome = 10000*d1 + 1000*d2 +100*d3 + 10*d2 + d1;
... deal with palindrome ...
}
}
}