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   "source": [
    "# [Array / String](https://leetcode.com/studyplan/leetcode-75/)"
   ]
  },
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    "## [151. Reverse Words in a String](https://leetcode.com/problems/reverse-words-in-a-string/description/?envType=study-plan-v2&envId=leetcode-75)\n",
    "\n",
    "Medium\n",
    "\n",
    "Given an input string s, reverse the order of the words.\n",
    "\n",
    "A word is defined as a sequence of non-space characters. The words in s will be separated by at least one space.\n",
    "\n",
    "Return a string of the words in reverse order concatenated by a single space.\n",
    "\n",
    "Note that s may contain leading or trailing spaces or multiple spaces between two words. The returned string should only have a single space separating the words. Do not include any extra spaces. \n",
    "\n",
    "Example 1:\n",
    "\n",
    "    Input: s = \"the sky is blue\"\n",
    "    Output: \"blue is sky the\"\n",
    "    \n",
    "Example 2:\n",
    "\n",
    "    Input: s = \"  hello world  \"\n",
    "    Output: \"world hello\"\n",
    "    Explanation: Your reversed string should not contain leading or trailing spaces.\n",
    "    \n",
    "Example 3:\n",
    "\n",
    "    Input: s = \"a good   example\"\n",
    "    Output: \"example good a\"\n",
    "    Explanation: You need to reduce multiple spaces between two words to a single space in the reversed string.\n",
    " \n",
    "Constraints:\n",
    "\n",
    "    1 <= s.length <= 104\n",
    "    s contains English letters (upper-case and lower-case), digits, and spaces ' '.\n",
    "    There is at least one word in s.\n",
    " \n",
    "Follow-up: If the string data type is mutable in your language, can you solve it in-place with O(1) extra space?"
   ]
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    {
     "data": {
      "text/plain": [
       "'example good a'"
      ]
     },
     "execution_count": 3,
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    }
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   "source": [
    "import re\n",
    "\n",
    "def reverseWords(s: str) -> str:\n",
    "    return ' '.join(re.sub(r'\\s{2,}', ' ', s).strip().split(' ')[::-1])\n",
    "\n",
    "reverseWords('a good   example')"
   ]
  }
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