<分区>
这是真正的问题
https://www.codechef.com/problems/PRPALIN/
以下代码适用于所有输入，但输入 900000 时执行时间为 1.125 秒。我如何优化代码？如何改进代码？
非常感谢任何帮助。谢谢你! :)
#include <iostream>
#include <cmath>
#include <cassert>
#include <ctime>
clock_t start=clock();
long long a;
inline long long next_prime();
inline bool palindrome();
int main()
{
freopen("in.txt","r",stdin);
scanf("%ld", &a);
assert(1 <= a <= 1000000);
do
a = next_prime();
while(!palindrome());
printf("%ld\n",a);
fprintf(stderr,"time=%.3lfsec\n",0.001*(clock()-start));
return 0;
}
long long next_prime()
{
long long num = a;
num++;
while(1)
{
int flag = 0;
long long i;
long long z = sqrt(num);
for(i = 2; i <= z; i++)
if((num % i) == 0)
flag = 1;
if(flag == 0)
return num;
else
num++;
}
}
bool palindrome()
{
long long reverse_num = 0;
long long temp = a;
while(temp != 0)
{
reverse_num = reverse_num * 10;
reverse_num = reverse_num + temp % 10;
temp = temp/10;
}
if(a == reverse_num)
return true;
else
return false;
}