[LC-19] Remove Nth Node From End of List.ipynb

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    "Given a linked list, remove the nth node from the end of list and return its head.\n",
    "\n",
    "For example,\n",
    "\n",
    "   Given linked list: 1->2->3->4->5, and n = 2.\n",
    "\n",
    "   After removing the second node from the end, the linked list becomes 1->2->3->5."
   ]
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    "class ListNode:\n",
    "    def __init__ (self,x):\n",
    "        self.val = x\n",
    "        self.next = None\n",
    "def construct_list (array):\n",
    "    head = ListNode (0)\n",
    "    for i in range (len(array)):\n",
    "        if i==0:\n",
    "            head = ListNode (array[i])\n",
    "            tail = head\n",
    "        else:\n",
    "            tail.next = ListNode (array[i])\n",
    "            tail = tail.next\n",
    "    return head\n",
    "def print_list_array (l,arg):\n",
    "    p = l\n",
    "    temp = []\n",
    "    while p:\n",
    "        temp.append(p.val)\n",
    "        p = p.next\n",
    "    print (arg,temp)"
   ]
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  {
   "cell_type": "code",
   "execution_count": 29,
   "metadata": {
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   "outputs": [],
   "source": [
    "l = construct_list ([1,2,3])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "metadata": {
    "collapsed": true
   },
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   "source": [
    "def removeNthFromEnd(head, n):\n",
    "        fast = slow = head\n",
    "        for i in range (n):\n",
    "            fast = fast.next \n",
    "        if not fast:\n",
    "            return head.next\n",
    "        while fast.next:\n",
    "            fast = fast.next\n",
    "            slow = slow.next\n",
    "        \n",
    "        slow.next = slow.next.next\n",
    "        return head"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 30,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "l1 = removeNthFromEnd(l,3)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 31,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "('result', [2, 3])\n"
     ]
    }
   ],
   "source": [
    "print_list_array (l1,\"result\")"
   ]
  }
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