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    "<h1>344. Reverse String</h1>\n",
    "<hr>\n",
    "\n",
    "<!--Copy Paste Leetcode statement between-->\n",
    "<p>Write a function that reverses a string. The input string is given as an array of characters <code>char[]</code>.</p>\n",
    "\n",
    "<p>Do not allocate extra space for another array, you must do this by <strong>modifying the input array&nbsp;<a href=\"https://en.wikipedia.org/wiki/In-place_algorithm\" target=\"_blank\">in-place</a></strong> with O(1) extra memory.</p>\n",
    "\n",
    "<p>You may assume all the characters consist of <a href=\"https://en.wikipedia.org/wiki/ASCII#Printable_characters\" target=\"_blank\">printable ascii characters</a>.</p>\n",
    "\n",
    "<p>&nbsp;</p>\n",
    "\n",
    "<div>\n",
    "<p><strong>Example 1:</strong></p>\n",
    "\n",
    "<pre><strong>Input: </strong><span id=\"example-input-1-1\">[\"h\",\"e\",\"l\",\"l\",\"o\"]</span>\n",
    "<strong>Output: </strong><span id=\"example-output-1\">[\"o\",\"l\",\"l\",\"e\",\"h\"]</span>\n",
    "</pre>\n",
    "\n",
    "<div>\n",
    "<p><strong>Example 2:</strong></p>\n",
    "\n",
    "<pre><strong>Input: </strong><span id=\"example-input-2-1\">[\"H\",\"a\",\"n\",\"n\",\"a\",\"h\"]</span>\n",
    "<strong>Output: </strong><span id=\"example-output-2\">[\"h\",\"a\",\"n\",\"n\",\"a\",\"H\"]</span>\n",
    "</pre>\n",
    "</div>\n",
    "</div>\n",
    "<!--Copy Paste Leetcode statement between-->\n",
    "\n",
    "<p>&nbsp;</p>\n",
    "<a href=\"https://leetcode.com/problems/reverse-string/\">Source</a> \n",
    "<hr>\n",
    "\n",
    "<h4>Code</h4>"
   ]
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   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "def reverse_list(stringlist):\n",
    "    \"\"\"Iterative approach\"\"\"\n",
    "    if not stringlist:\n",
    "        return\n",
    "    left = 0\n",
    "    right = len(stringlist)-1\n",
    "    while left < right:\n",
    "        stringlist[left], stringlist[right] = stringlist[right], stringlist[left]\n",
    "        left += 1\n",
    "        right -= 1\n",
    "    return stringlist"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [],
   "source": [
    "def reverse_list(stringlist):\n",
    "    \"\"\"Iterative approach\"\"\"\n",
    "    n = len(stringlist)\n",
    "    # base case\n",
    "    if n <= 1:\n",
    "        return stringlist\n",
    "    # recursion\n",
    "    return(reverse_list(stringlist[n//2:]) + reverse_list(stringlist[:n//2]))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [],
   "source": [
    "def reverse_list(stringlist):\n",
    "    \"\"\"cheating\"\"\"\n",
    "    mylist[:] = mylist[::-1]  # modified in place\n",
    "    # return mylist[::-1] # NOT modified in place"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<h4>Check</h4>"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['o', 'l', 'l', 'e', 'h']"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "stringlist = [\"h\",\"e\",\"l\",\"l\",\"o\"]\n",
    "reverse_list(stringlist)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['h', 'a', 'n', 'n', 'a', 'H']"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "stringlist = [\"H\",\"a\",\"n\",\"n\",\"a\",\"h\"]\n",
    "reverse_list(stringlist)"
   ]
  }
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