[USACO1.5]回文质数 Prime Palindromes

https://www.luogu.org/problemnew/show/P1217

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
using namespace std;
typedef long long ll;
typedef __int128 lll;
const int N=100000000+1000;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,q;
int prime[N];
bool pp[N];
int vis[N];
bool pd_h(int x)
{

    int y=x,num=0;//int y=x,防止x被改变
    while (y!=0)
    {
        num=num*10+y%10;//上一次数字的记录进位再加上下一位数
        y/=10;
    }
    if (num==x) return 1;
    else return 0;
}

int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    //scanf("%d",&n);
    int a,b;
    cin>>a>>b;
    int cnt=0;
    if(b>10000000) b=10000000;
    for(int i=2;i<=b;i++)
    {
        if(!vis[i]) prime[cnt++]=i,pp[i]=1;
        for(int j=0;j<cnt&&i*prime[j]<=b;j++)
        {
            vis[i*prime[j]]=i;
            if(i%prime[j]==0) break;
        }
    }
    for(int i=a;i<=b;i++)
    {
        if(i>10000000) break;
        if(pd_h(i)&&pp[i]) printf("%d\n",i);
    }
    //cout << "Hello world!" << endl;
    return 0;
}