DSA/hashtable/intersect.ipynb

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    "Given two arrays, write a function to compute their intersection.\n",
    "\n",
    "Example 1:\n",
    "\n",
    "    Input: nums1 = [1,2,2,1], nums2 = [2,2]\n",
    "    Output: [2,2]\n",
    "Example 2:\n",
    "\n",
    "    Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4]\n",
    "    Output: [4,9]\n",
    "Note:\n",
    "\n",
    "- Each element in the result should appear as many times as it shows in both arrays.\n",
    "- The result can be in any order.\n",
    "\n",
    "Follow up:\n",
    "\n",
    "- What if the given array is already sorted? How would you optimize your algorithm?\n",
    "- What if nums1's size is small compared to nums2's size? Which algorithm is better?\n",
    "- What if elements of nums2 are stored on disk, and the memory is limited such that you cannot load all elements into the memory at once?"
   ]
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     "text": [
      "[2, 2]\n"
     ]
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    "class Solution:\n",
    "    def intersect(self, nums1, nums2):\n",
    "        '''\n",
    "        :param nums1: List[int]\n",
    "        :param nums2: List[int]\n",
    "        :return: List[int]\n",
    "        '''\n",
    "        from collections import Counter\n",
    "        a, b = Counter(nums1), Counter(nums2)\n",
    "        res = []\n",
    "        for i in a:\n",
    "            if i in b:\n",
    "                tmp = min(a[i],b[i])\n",
    "                while tmp:\n",
    "                    res.append(i)\n",
    "                    tmp -= 1\n",
    "        return res\n",
    "        \n",
    "# test\n",
    "a = [1,2,2,1]\n",
    "b = [2,2]\n",
    "print(Solution().intersect(a,b))"
   ]
  }
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