usaco1.52Prime Palindromes

dfs搜前5位数 根据前面的算后面的

/*
 ID: your_id_here
 PROG: pprime
 LANG: C++
 */
#include <iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;
int a,b,g;
int kk[10000],f[20][20],tt,ff[100000];
char s[20];
int prime(int x)
{
    int i,j,k,flag = 1;
    k = sqrt(x);
    for(i = 2 ; i <= k ; i++)
    {
        if(x%i==0)
        {
            flag = 0;
            break;
        }
    }
    return flag;
}
int palind(int k,char *ss)
{
    int i,flag = 1;
    for(i = 1; i <= k ;i++)
    if(ss[i]!=ss[k-i+1])
    {
        flag = 0;
        break;
    }
    return flag;
}
void dfs(int v)
{
    int i,y,s1 =0,s2 =0,s3 = 0,j;
    char str[20],str3[20];
    if(v>5)
    return ;
    for(i = 1; i <= v ; i++)
    str[i] = s[i];
    for(i = 1; i <= v ; i++)
    str3[i] = s[i];
    j = v;
    for(i = v+1 ; i <= 2*v ; i++)
    str[i] = s[j--];
    j = v-1;
    for(i = v+1 ; i < 2*v ; i++)
    str3[i] = s[j--];
    y = 1;
    for(i = v; i >= 1 ; i--)
    {
        s1+=y*(s[i]-'0');
        y = y*10;
    }
    y = 1;
    for(i = 2*v ; i >= 1 ; i--)
    {
        s2+=y*(str[i]-'0');
        y = y*10;
    }
    y = 1;
    for(i = 2*v-1 ; i >= 1 ; i--)
    {
        s3+=y*(str3[i]-'0');
        y = y*10;
    }
    if(s1>=a&&s1<=b)
    {
        if(palind(v,s)&&prime(s1))
        {
            if(s1<100000)
            {
                if(!ff[s1])
                {
                    g++;
                    kk[g] = s1;
                    ff[s1] = 1;
                }
            }
            else
            {
                g++;
                kk[g] = s1;
            }
        }
    }
    if(s2>=a&&s2<=b)
    {
        if(palind(2*v,str)&&prime(s2))
        {
            if(s2<100000)
            {
                if(!ff[s2])
                {
                    g++;
                    kk[g] = s2;
                    ff[s2] = 1;
                }
            }
            else
            {

                g++;
                kk[g] = s2;
            }
        }
    }
    if(s3>=a&&s3<=b)
    {
        if(palind(2*v-1,str3)&&prime(s3))
        {

            if(s3<100000)
            {
                if(!ff[s3])
                {
                    g++;
                    kk[g] = s3;
                    ff[s3] = 1;
                }
            }
            else
            {
                g++;
                kk[g] = s3;
            }
        }
    }
    if(s1>b)
    return ;
    for(i = 0 ; i <= 9 ; i++)
    {
        s[v+1] = i+'0';
        dfs(v+1);
    }
}
int main()
{
    freopen("pprime.in","r",stdin);
    freopen("pprime.out","w",stdout);
    int i;
    char num[20];
    cin>>a>>b;
    for(i = 1; i <= 9 ; i++)
    {
        s[1] = i+'0';
        dfs(1);
    }
    sort(kk+1,kk+g+1);
    for(i = 1; i <= g ; i++)
    cout<<kk[i]<<endl;
    fclose(stdin);
    fclose(stdout);
    return 0;
}