Project Euler Q37 - LO Man Hei

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    "### Q37\n",
    "Find the sum of the only eleven primes that are both truncatable from left to right and right to left."
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    "def prime_numbers(n, max_len = False):\n",
    "    result = []\n",
    "    if max_len:\n",
    "        n = max_len**2//5000 + max_len*20\n",
    "    sieve = [True] * (n+1)\n",
    "    for p in range(2, n+1):\n",
    "        if (sieve[p]):\n",
    "            result.append(p)\n",
    "            if max_len and len(result) >= max_len:\n",
    "                return result\n",
    "            for i in range(p, n+1, p):\n",
    "                sieve[i] = False\n",
    "    return result\n",
    "\n",
    "def is_prime(n,prime_list,search_range):\n",
    "    if n < search_range:\n",
    "        if n in prime_list:\n",
    "            return True\n",
    "        else:\n",
    "            return False\n",
    "    for i in range(2,n):\n",
    "        if (n%i) == 0:\n",
    "            return False\n",
    "    return True\n",
    "\n",
    "def truncatable_primes(max_len = 11, search_range = 1000000):\n",
    "    prime_list = set(prime_numbers(search_range))\n",
    "    result = []\n",
    "    for p in prime_list:\n",
    "        str_p = str(p)\n",
    "        len_p = len(str_p)\n",
    "        if len_p < 2 or any(i in str_p[1:] for i in ['2','4','6','8','0']) or str_p[0] in ['1','4','6','8','9'] or str_p[-1] in ['1','5','9']:\n",
    "            continue\n",
    "        for i in range(1,len_p):\n",
    "            if not is_prime(int(str_p[i:]),prime_list,search_range) or not is_prime(int(str_p[:i]),prime_list,search_range):\n",
    "                break\n",
    "        else:\n",
    "            result.append(p)\n",
    "            if len(result) == max_len:\n",
    "                break\n",
    "    return result\n"
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     "text": [
      "CPU times: user 148 ms, sys: 0 ns, total: 148 ms\n",
      "Wall time: 145 ms\n"
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     "data": {
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       "748317"
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   "source": [
    "%%time\n",
    "sum(truncatable_primes())"
   ]
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   "id": "3d047ff9-52dc-4b20-b614-4192212ea5ad",
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