Prime Palindromes

#include <cstdio>
#include <vector>
#include <string>
#include <math.h>
#include <fstream>
#include <algorithm>
#include <iostream>

using namespace std;

// Generate the palindromes
void gen(int seed, int parity, int l, int h, vector<int> & palindromes){
    // Generates a single palindrome
    // parity = 0: even length
    // parity = 1: odd length

    string str = to_string(seed);
    string reversed = str.substr(0,str.length()-parity);
    reverse(reversed.begin(),reversed.end());

    int pal = stoi(str+reversed);
    if(pal>=l && pal<=h){
        palindromes.push_back(pal);
    }
}

void generate(int l, int h, vector<int> & palindromes){
    for(int j=0; j<4; j++){
        for(int i=pow(10,j); i<pow(10,j+1); i++){
            gen(i,0,l,h,palindromes);
            gen(i,1,l,h,palindromes);
        }
    }
}

// Get the primes
void getPrimes(vector<int> palindromes, vector<int> & primes){
    bool k;
    for(int pal:palindromes){
        k = true;
        for(int fact=2;fact<sqrt(pal)+1;fact++){
            if(pal%fact == 0){
                k=false;
                break;
            }
        }
        if(k==true){
            primes.push_back(pal);
        }
    }
}

// Main, obviously
int main(){
    // Read the input file
    ifstream fIn("pprime.in");
    int l, h;
    fIn >> l >> h;
    fIn.close();

    // Do the important things
    vector<int> palindromes;
    vector<int> primes;
    generate(l, h, palindromes);
    getPrimes(palindromes,primes);
    sort(primes.begin(),primes.end());

    // Write the output file
    ofstream fOut("pprime.out");
    for(int i:primes){
        fOut << i << endl;
    }
    fOut.close();
    return 0;   
}