algorithms/217-contains-duplicate.ipynb

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    "### [存在重复元素](https://leetcode-cn.com/problems/contains-duplicate/)\n",
    "\n",
    "给定一个整数数组，判断是否存在重复元素。\n",
    "\n",
    "如果存在一值在数组中出现至少两次，函数返回 true 。如果数组中每个元素都不相同，则返回 false 。\n",
    "\n",
    "#### 示例 1:\n",
    "```\n",
    "输入: [1,2,3,1]\n",
    "输出: true\n",
    "```\n",
    "\n",
    "#### 示例 2:\n",
    "```\n",
    "输入: [1,2,3,4]\n",
    "输出: false\n",
    "```\n",
    "\n",
    "#### 示例 3:\n",
    "```\n",
    "输入: [1,1,1,3,3,4,3,2,4,2]\n",
    "输出: true\n",
    "```"
   ]
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  {
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   "execution_count": 5,
   "id": "split-provincial",
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   "source": [
    "from typing import List\n",
    "\n",
    "def containsDuplicate(nums: List[int]) -> bool:\n",
    "    s = set()\n",
    "    for num in nums:\n",
    "        if num in s:\n",
    "            return True\n",
    "        else:\n",
    "            s.add(num)\n",
    "    return False"
   ]
  },
  {
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   "execution_count": 6,
   "id": "ceramic-pension",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "containsDuplicate([1,2,3,1])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "id": "nervous-position",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "False"
      ]
     },
     "execution_count": 7,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "containsDuplicate([1,2,3,4])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "id": "blocked-houston",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "containsDuplicate([1,1,1,3,3,4,3,2,4,2])"
   ]
  }
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