15 - 3Sum.ipynb

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      "[[-3, 1, 2], [-2, 0, 2], [-2, 1, 1], [-1, 0, 1]]\n",
      "[[-5, 2, 3], [-2, -1, 3]]\n"
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    "\n",
    "'''\n",
    "15 - 3Sum\n",
    "\n",
    "Given an integer array nums, return all the triplets [nums[i], nums[j], nums[k]] \n",
    "such that i != j, i != k, and j != k, and nums[i] + nums[j] + nums[k] == 0.\n",
    "\n",
    "Notice that the solution set must not contain duplicate triplets.\n",
    "'''\n",
    "\n",
    "def threeSum(nums):\n",
    "    res=[]\n",
    "\n",
    "    #Sorting the array \n",
    "    nums.sort()\n",
    "\n",
    "    for i in range(len(nums)):\n",
    "\n",
    "        #If current value is same as the previous one skip it to exclude duplicate triplets\n",
    "        if i>0 and nums[i] == nums[i-1]:\n",
    "            continue\n",
    "\n",
    "        #Proceeding with two sum\n",
    "        #Setting left and right pointers\n",
    "        l,r = i+1 , len(nums)-1\n",
    "\n",
    "        while l<r:\n",
    "            total= nums[i] + nums[l] + nums[r]\n",
    "\n",
    "            if total == 0:\n",
    "                res.append([nums[i], nums[l],nums[r]])\n",
    "                l += 1\n",
    "                while nums[l] == nums[l-1] and l<r:\n",
    "                    l+=1\n",
    "            elif total>0:\n",
    "                r -= 1\n",
    "            else:\n",
    "                l += 1\n",
    "\n",
    "    return res  \n",
    "\n",
    "def main():\n",
    "    \n",
    "    print(threeSum([-3, 0, 1, 2, -1, 1, -2]))\n",
    "    print(threeSum([-5, 2, -1, -2, 3]))\n",
    "\n",
    "\n",
    "main()\n",
    "\n",
    "\n"
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