Posted on 2012-09-22 17:45
hoshelly 閱讀(310)
評(píng)論(0) 編輯 收藏 引用 所屬分類:
Programming
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 <= 1000,000,000); both a and b are considered to be within the range .
Input
Line 1: Two integers, a and b
Output
The list of palindromic primes in numerical order, one per line.
Sample Input
5 500
Sample Output
5
7
11
101
131
151
181
191
313
353
373
383
#include<stdio.h>
#include<math.h>
#include<stdlib.h>
int i;
int Is_Prime(int a)
{
double t = a;
for(i=2;i<=sqrt(t);i++)
{
if(a % i == 0)
return 0;
}
return 1;
}
int diglen(int c)
{
if(c/10 == 0)
return 1;
int count=0;
while(c)
{
c=c/10;
count++;
}
return count;
}
void IntoStr(int a,char* str) //將數(shù)字轉(zhuǎn)換為字符串
{
int h= diglen(a)-1,i=0;
while(h+1)
{
int k,c,d=1;
for(k=0;k<h;k++)
{
d=d*10;
}
c=a/d;//取本次數(shù)字的最高位
str[i++] = c+48;
a = a%d; //取余數(shù)
h--;
}
str[i]='\0'; //最后末尾加字符串結(jié)束符
}
int Is_Pal(int b)
{
int len = diglen(b);
int ok = 1,j;
char* str = (char*)malloc(sizeof(char)*(len+1));
IntoStr(b,str); //將數(shù)字轉(zhuǎn)換為字符數(shù)組，也可以用itoa函數(shù)或 sprintf函數(shù)
for(i=0,j=len-1;i < len/2;i++,j--)
{
if(str[i] != str[j])
ok = 0;
}
free(str);
if(ok == 1)
return 1;
else
return 0;
}
int main()
{
int a,b,j;
scanf("%d%d",&a,&b);
for(j=a;j<=b;j++)
{
if(Is_Prime(j) && Is_Pal(j))
printf("%d\n",j);
}
return 0;
}