0092_Problem_3.cpp

// code_report Solution
// https://youtu.be/nHI0SVNbhdY

// GENERATING CODE

#include <string>
#include <algorithm>
#include <iostream>

using namespace std;

bool is_prime (int n) {
   if (n < 2 || n % 2 == 0) return n == 2;
   for (int i = 3; i * i <= n; i += 2)
      if (n % i == 0) return false;
   return true;
}

bool is_prime_palindrome (int n) {
   auto s = to_string (n), t = s;
   reverse (s.begin (), s.end ());
   return (s == t && is_prime (n));
}

void skip (int& i) {
   ++i;
   if (i == 1000   ||
       i == 100000 ||
       i == 10000000) i *= 10;
   int j = i, k = 1; // j = first digit, k = num digits
   while (j >= 10) j /= 10, ++k;
   if ((j % 2 == 0 || j == 5) && k > 1) i += pow (10, k - 1);
}

int main () 
{
   for (int i = 1; i <= 2 * pow (10, 8); skip (i)) {
      if (is_prime_palindrome (i)) {
         cout << i << ",";
         if (i > pow (10, 8)) break;
      }
   }

   return 0;
}

// SUBMISSION CODE:

#include <set>

class Solution {
public:
   int primePalindrome (int N) {
      set<int> s {2,3,5,7,11,101,131,151,181,191,313,353,373,383,727,757,787,797,919,929,10301,
         10501,10601,11311,11411,12421,12721,12821,13331,13831,13931,14341,14741,15451,15551,16061,
         16361,16561,16661,17471,17971,18181,18481,19391,19891,19991,30103,30203,30403,30703,30803,
         31013,31513,32323,32423,33533,34543,34843,35053,35153,35353,35753,36263,36563,37273,37573,
         38083,38183,38783,39293,70207,70507,70607,71317,71917,72227,72727,73037,73237,73637,74047,
         74747,75557,76367,76667,77377,77477,77977,78487,78787,78887,79397,79697,79997,90709,91019,
         93139,93239,93739,94049,94349,94649,94849,94949,95959,96269,96469,96769,97379,97579,97879,
         98389,98689,1003001,1008001,1022201,1028201,1035301,1043401,1055501,1062601,1065601,1074701,
         1082801,1085801,1092901,1093901,1114111,1117111,1120211,1123211,1126211,1129211,1134311,
         1145411,1150511,1153511,1160611,1163611,1175711,1177711,1178711,1180811,1183811,1186811,
         1190911,1193911,1196911,1201021,1208021,1212121,1215121,1218121,1221221,1235321,1242421,
         1243421,1245421,1250521,1253521,1257521,1262621,1268621,1273721,1276721,1278721,1280821,
         1281821,1286821,1287821,1300031,1303031,1311131,1317131,1327231,1328231,1333331,1335331,
         1338331,1343431,1360631,1362631,1363631,1371731,1374731,1390931,1407041,1409041,1411141,
         1412141,1422241,1437341,1444441,1447441,1452541,1456541,1461641,1463641,1464641,1469641,
         1486841,1489841,1490941,1496941,1508051,1513151,1520251,1532351,1535351,1542451,1548451,
         1550551,1551551,1556551,1557551,1565651,1572751,1579751,1580851,1583851,1589851,1594951,
         1597951,1598951,1600061,1609061,1611161,1616161,1628261,1630361,1633361,1640461,1643461,
         1646461,1654561,1657561,1658561,1660661,1670761,1684861,1685861,1688861,1695961,1703071,
         1707071,1712171,1714171,1730371,1734371,1737371,1748471,1755571,1761671,1764671,1777771,
         1793971,1802081,1805081,1820281,1823281,1824281,1826281,1829281,1831381,1832381,1842481,
         1851581,1853581,1856581,1865681,1876781,1878781,1879781,1880881,1881881,1883881,1884881,
         1895981,1903091,1908091,1909091,1917191,1924291,1930391,1936391,1941491,1951591,1952591,
         1957591,1958591,1963691,1968691,1969691,1970791,1976791,1981891,1982891,1984891,1987891,
         1988891,1993991,1995991,1998991,3001003,3002003,3007003,3016103,3026203,3064603,3065603,
         3072703,3073703,3075703,3083803,3089803,3091903,3095903,3103013,3106013,3127213,3135313,
         3140413,3155513,3158513,3160613,3166613,3181813,3187813,3193913,3196913,3198913,3211123,
         3212123,3218123,3222223,3223223,3228223,3233323,3236323,3241423,3245423,3252523,3256523,
         3258523,3260623,3267623,3272723,3283823,3285823,3286823,3288823,3291923,3293923,3304033,
         3305033,3307033,3310133,3315133,3319133,3321233,3329233,3331333,3337333,3343433,3353533,
         3362633,3364633,3365633,3368633,3380833,3391933,3392933,3400043,3411143,3417143,3424243,
         3425243,3427243,3439343,3441443,3443443,3444443,3447443,3449443,3452543,3460643,3466643,
         3470743,3479743,3485843,3487843,3503053,3515153,3517153,3528253,3541453,3553553,3558553,
         3563653,3569653,3586853,3589853,3590953,3591953,3594953,3601063,3607063,3618163,3621263,
         3627263,3635363,3643463,3646463,3670763,3673763,3680863,3689863,3698963,3708073,3709073,
         3716173,3717173,3721273,3722273,3728273,3732373,3743473,3746473,3762673,3763673,3765673,
         3768673,3769673,3773773,3774773,3781873,3784873,3792973,3793973,3799973,3804083,3806083,
         3812183,3814183,3826283,3829283,3836383,3842483,3853583,3858583,3863683,3864683,3867683,
         3869683,3871783,3878783,3893983,3899983,3913193,3916193,3918193,3924293,3927293,3931393,
         3938393,3942493,3946493,3948493,3964693,3970793,3983893,3991993,3994993,3997993,3998993,
         7014107,7035307,7036307,7041407,7046407,7057507,7065607,7069607,7073707,7079707,7082807,
         7084807,7087807,7093907,7096907,7100017,7114117,7115117,7118117,7129217,7134317,7136317,
         7141417,7145417,7155517,7156517,7158517,7159517,7177717,7190917,7194917,7215127,7226227,
         7246427,7249427,7250527,7256527,7257527,7261627,7267627,7276727,7278727,7291927,7300037,
         7302037,7310137,7314137,7324237,7327237,7347437,7352537,7354537,7362637,7365637,7381837,
         7388837,7392937,7401047,7403047,7409047,7415147,7434347,7436347,7439347,7452547,7461647,
         7466647,7472747,7475747,7485847,7486847,7489847,7493947,7507057,7508057,7518157,7519157,
         7521257,7527257,7540457,7562657,7564657,7576757,7586857,7592957,7594957,7600067,7611167,
         7619167,7622267,7630367,7632367,7644467,7654567,7662667,7665667,7666667,7668667,7669667,
         7674767,7681867,7690967,7693967,7696967,7715177,7718177,7722277,7729277,7733377,7742477,
         7747477,7750577,7758577,7764677,7772777,7774777,7778777,7782877,7783877,7791977,7794977,
         7807087,7819187,7820287,7821287,7831387,7832387,7838387,7843487,7850587,7856587,7865687,
         7867687,7868687,7873787,7884887,7891987,7897987,7913197,7916197,7930397,7933397,7935397,
         7938397,7941497,7943497,7949497,7957597,7958597,7960697,7977797,7984897,7985897,7987897,
         7996997,9002009,9015109,9024209,9037309,9042409,9043409,9045409,9046409,9049409,9067609,
         9073709,9076709,9078709,9091909,9095909,9103019,9109019,9110119,9127219,9128219,9136319,
         9149419,9169619,9173719,9174719,9179719,9185819,9196919,9199919,9200029,9209029,9212129,
         9217129,9222229,9223229,9230329,9231329,9255529,9269629,9271729,9277729,9280829,9286829,
         9289829,9318139,9320239,9324239,9329239,9332339,9338339,9351539,9357539,9375739,9384839,
         9397939,9400049,9414149,9419149,9433349,9439349,9440449,9446449,9451549,9470749,9477749,
         9492949,9493949,9495949,9504059,9514159,9526259,9529259,9547459,9556559,9558559,9561659,
         9577759,9583859,9585859,9586859,9601069,9602069,9604069,9610169,9620269,9624269,9626269,
         9632369,9634369,9645469,9650569,9657569,9670769,9686869,9700079,9709079,9711179,9714179,
         9724279,9727279,9732379,9733379,9743479,9749479,9752579,9754579,9758579,9762679,9770779,
         9776779,9779779,9781879,9782879,9787879,9788879,9795979,9801089,9807089,9809089,9817189,
         9818189,9820289,9822289,9836389,9837389,9845489,9852589,9871789,9888889,9889889,9896989,
         9902099,9907099,9908099,9916199,9918199,9919199,9921299,9923299,9926299,9927299,9931399,
         9932399,9935399,9938399,9957599,9965699,9978799,9980899,9981899,9989899,100030001};

      return *s.lower_bound (N);
   }
};