PalindromePrime | Topcoder Archive

Problem Statement

A positive integer is called a prime if it has exactly two distinct positive integer divisors: 1 and itself. The first few primes are 2, 3, 5, 7, 11, 13, ...

A positive integer is called a palindrome if its base-10 representation reads the same forwards and backwards. Some palindromes: 2, 77, 101, 33333, 12344321.

A positive integer is called a palindromic prime if it is both a palindrome and a prime.

You are given two ints: L and R. Compute and return the number of palindromic primes between L and R, inclusive.

Definition

Class:: PalindromePrime
Method:: count
Parameters:: int, int
Returns:: int
Method signature:: int count(int L, int R)
(be sure your method is public)

Notes

The number 1 is not a prime number.

Constraints

L will be between 1 and 1,000, inclusive.
R will be between L and 1,000, inclusive.

Examples

```
100
```
```
150
```
```
Returns: 2
```
This range contains only two palindromic primes: 101 and 131.
```
1
```
```
9
```
```
Returns: 4
```
The palindromic primes in this range are 2, 3, 5, and 7.
```
929
```
```
929
```
```
Returns: 1
```
```
1
```
```
1
```
```
Returns: 0
```
```
1
```
```
1000
```
```
Returns: 20
```

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