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   "source": [
    "Given a string `s`, return  _the longest palindromic substring_ in `s`.\n",
    "\n",
    "\n",
    "\n",
    "**Example 1:**\n",
    "\n",
    "\n",
    "\n",
    "    Input: s = \"babad\"\n",
    "    Output: \"bab\"\n",
    "    **Note:** \"aba\" is also a valid answer.\n",
    "\n",
    "\n",
    "**Example 2:**\n",
    "\n",
    "\n",
    "\n",
    "    Input: s = \"cbbd\"\n",
    "    Output: \"bb\"\n",
    "\n",
    "\n",
    "**Example 3:**\n",
    "\n",
    "\n",
    "\n",
    "    Input: s = \"a\"\n",
    "    Output: \"a\"\n",
    "\n",
    "\n",
    "**Example 4:**\n",
    "\n",
    "\n",
    "\n",
    "    Input: s = \"ac\"\n",
    "    Output: \"a\"\n",
    "\n",
    "\n",
    "\n",
    "\n",
    "**Constraints:**\n",
    "\n",
    "  * `1 <= s.length <= 1000`\n",
    "  * `s` consist of only digits and English letters (lower-case and/or upper-case),"
   ],
   "metadata": {}
  },
  {
   "outputs": [
    {
     "output_type": "execute_result",
     "data": {
      "text/plain": "_longest_palindrome (generic function with 1 method)"
     },
     "metadata": {},
     "execution_count": 1
    }
   ],
   "cell_type": "code",
   "source": [
    "# @lc code=start\n",
    "using LeetCode\n",
    "\n",
    "function longest_palindrome(s::String)::AbstractString\n",
    "    res = \"\"\n",
    "    for i in 1:length(s)\n",
    "        s_odd = _longest_palindrome(s, i, i)\n",
    "        if length(s_odd) > length(res)\n",
    "            res = s_odd\n",
    "        end\n",
    "        s_even = _longest_palindrome(s, i, i + 1)\n",
    "        if length(s_even) > length(res)\n",
    "            res = s_even\n",
    "        end\n",
    "    end\n",
    "    return res\n",
    "end\n",
    "\n",
    "function _longest_palindrome(s, l, r)\n",
    "    while l >= 1 && r <= length(s) && s[l] == s[r]\n",
    "        l -= 1\n",
    "        r += 1\n",
    "    end\n",
    "    return SubString(s, l + 1, r - 1)\n",
    "end\n",
    "# @lc code=end"
   ],
   "metadata": {},
   "execution_count": 1
  },
  {
   "cell_type": "markdown",
   "source": [
    "---\n",
    "\n",
    "*This notebook was generated using [Literate.jl](https://github.com/fredrikekre/Literate.jl).*"
   ],
   "metadata": {}
  }
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