2013
12-30

# Palindromic Primes Category in Jeopardy!

Prime numbers are defined as follows: a number is prime if it is greater than 1 and is evenly divisible only by itself and 1. Note that by definition neither zero nor one is a prime number.
A palindromic number is one whose string representation is a palindrome, that is, a string that reads the same backwards and forwards.
You are on the clue crew preparing questions for the category “Palindromic Primes” and are to write a program to generate the answer and responding question in Jeopardy! style.

The input file contains a series of number pairs (with white space separating them) specifying individual problems, ending with a pair of zeroes. The first number gives the number of digits for the numbers to be considered, the second number gives the base in which the numbers are to be generated. The numbers are separated by a single space. You are assured that all palindromic primes for this problem can be represented in the range of a standard 32-bit signed integer. The bases allowed are integer bases between 2 and 36 ― with bases above base ten handled as extensions of hexadecimal. This means that the valid numeric digits are in the range [‘0’..‘9’] and [‘a’..‘z’].

The input file contains a series of number pairs (with white space separating them) specifying individual problems, ending with a pair of zeroes. The first number gives the number of digits for the numbers to be considered, the second number gives the base in which the numbers are to be generated. The numbers are separated by a single space. You are assured that all palindromic primes for this problem can be represented in the range of a standard 32-bit signed integer. The bases allowed are integer bases between 2 and 36 ― with bases above base ten handled as extensions of hexadecimal. This means that the valid numeric digits are in the range [‘0’..‘9’] and [‘a’..‘z’].

1 10
2 10
3 10
4 24
5 4
0 0

The number of 1-digit palindromic primes < 2^31 in base 10.
What is 4?

The number of 2-digit palindromic primes < 2^31 in base 10.
What is 1?

The number of 3-digit palindromic primes < 2^31 in base 10.
What is 15?

The number of 4-digit palindromic primes < 2^31 in base 24.
What is 0?

The number of 5-digit palindromic primes < 2^31 in base 4.
What is 10?

2. 算法是程序的灵魂，算法分简单和复杂，如果不搞大数据类，程序员了解一下简单点的算法也是可以的，但是会算法的一定要会编程才行，程序员不一定要会算法，利于自己项目需要的可以简单了解。

3. 学算法中的数据结构学到一定程度会乐此不疲的，比如其中的2－3树，类似的红黑树，我甚至可以自己写个逻辑文件系统结构来。

4. int half(int *array,int len,int key)
{
int l=0,r=len;
while(l<r)
{
int m=(l+r)>>1;
if(key>array )l=m+1;
else if(key<array )r=m;
else return m;
}
return -1;
}
这种就能避免一些Bug
l,m,r
左边是l,m;右边就是m+1,r;