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"cell_type": "heading",
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"source": [
"Chapter 10 : 2-3-4 Trees and External Storage"
]
},
{
"cell_type": "heading",
"level": 3,
"metadata": {},
"source": [
"Example 10.1 Page No : 478"
]
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"input": [
" \n",
"class DataItem:\n",
" def __init__(self,dd):\n",
" self.dData = dd\n",
"\n",
" def displayItem(self):\n",
" print '/' ,self.dData\n",
"\n",
"class Node:\n",
" def __init__(self):\n",
" self.ORDER = 4\n",
" self.numItems = 0\n",
" self.parent = None\n",
" self.childArray = [None,None,None,None]\n",
" self.itemArray = [None,None,None]\n",
"\n",
" def connectChild(self,childNum,child):\n",
" self.childArray[childNum] = child\n",
" if(child != None):\n",
" child.parent = self\n",
"\n",
" def disconnectChild(self,childNum):\n",
" tempNode = self.childArray[childNum]\n",
" self.childArray[childNum] = None\n",
" return tempNode\n",
"\n",
" def getChild(self,childNum):\n",
" return self.childArray[childNum]\n",
"\n",
" def getParent(self):\n",
" return self.parent\n",
"\n",
" def isLeaf(self):\n",
" if self.childArray[0]==None:\n",
" return True \n",
" return False \n",
"\n",
" def getNumItems(self):\n",
" return self.numItems\n",
"\n",
" def getItem(self,index): # get DataItem at index\n",
" return self.itemArray[index] \n",
"\n",
" def isFull(self):\n",
" if self.numItems==self.ORDER-1:\n",
" return True\n",
" return False\n",
"\n",
" def findItem(self,key): # return index of # item (within node)\n",
" for j in range(self.ORDER-1): \n",
" if(self.itemArray[j] == None):\n",
" break\n",
" elif(self.itemArray[j].dData == key):\n",
" return j\n",
" return -1\n",
"\n",
" def insertItem(self,newItem):\n",
" #assumes node is not full\n",
" self.numItems += 1 # will add new item\n",
" newKey = newItem.dData # key of new item\n",
" j = self.ORDER - 2\n",
" while j>=0:\n",
" if(self.itemArray[j] == None):\n",
" continue\n",
" else:\n",
" itsKey = self.itemArray[j].dData\n",
" if(newKey < itsKey):\n",
" self.itemArray[j+1] = self.itemArray[j]\n",
" else:\n",
" self.itemArray[j+1] = newItem\n",
" return j+1 # return index to\n",
" j -= 1\n",
"\n",
" self.itemArray[0] = newItem # insert new item\n",
" return 0\n",
"\n",
" def removeItem(self): # remove largest item\n",
" temp = self.itemArray[self.numItems-1] # save item\n",
" self.itemArray[self.numItems-1] = None # disconnect it\n",
" self.numItems -= 1 # one less item\n",
" return temp # return item\n",
"\n",
" def displayNode(self):\n",
" for j in range(self.numItems):\n",
" self.itemArray[j].displayItem()\n",
" print ''\n",
"\n",
"class Tree234:\n",
" def __init__(self):\n",
" self.root = Node() # make root node\n",
"\n",
" def find(self,key):\n",
" curNode = self.root\n",
" childNumber = 0\n",
" while(True):\n",
" childNumber=curNode.findItem(key) \n",
" if(childNumber != -1):\n",
" return childNumber # found it\n",
" elif( curNode.isLeaf() ):\n",
" return -1 # cant find it\n",
" else: # search deeper\n",
" curNode = getNextChild(curNode, key)\n",
"\n",
" def insert(self,dValue):\n",
" curNode = self.root\n",
" tempItem = DataItem(dValue)\n",
" while(True):\n",
" if( curNode.isFull() ):\n",
" split(curNode)\n",
" curNode = curNode.getParent()\n",
" curNode = getNextChild(curNode, dValue)\n",
" elif( curNode.isLeaf() ): # if node is leaf,\n",
" break\n",
" else:\n",
" curNode = getNextChild(curNode, dValue)\n",
" curNode.insertItem(tempItem)\n",
"\n",
" def split(self,thisNode): # split the node\n",
" # assumes node is full\n",
" itemC = thisNode.removeItem() # remove items from\n",
" itemB = thisNode.removeItem() # this node\n",
" child2 = thisNode.disconnectChild(2) # remove children\n",
" child3 = thisNode.disconnectChild(3) # from this nodeJava Code for a 2-3-4 Tree\n",
" newRight = Node() # make new node\n",
" if(thisNode==self.root):\n",
" self.root = Node()\n",
" parent = self.root\n",
" self.root.connectChild(0, thisNode)\n",
" else:\n",
" parent = thisNode.getParent()\n",
" itemIndex = parent.insertItem(itemB) # item B to parent\n",
" n = parent.getNumItems()\n",
" j = n-1\n",
" while j > itemIndex:\n",
" temp = parent.disconnectChild(j) # one child\n",
" parent.connectChild(j+1, temp)\n",
" j -= 1\n",
"\n",
" parent.connectChild(itemIndex+1, newRight) # deal with newRight\n",
" newRight.insertItem(itemC) # item C to newRight\n",
" newRight.connectChild(0, child2) # connect to 0 and 1\n",
" newRight.connectChild(1, child3) # on newRight\n",
"\n",
" def getNextChild(self,theNode,theValue):\n",
" # assumes node is not empty, not full, not a leaf\n",
" numItems = theNode.getNumItems() \n",
" for j in range(numItems): # for each item in node\n",
" if( theValue < theNode.getItem(j).dData ):\n",
" return theNode.getChild(j) # return left child\n",
" return theNode.getChild(j)\n",
"\n",
" def displayTree(self):\n",
" self.recDisplayTree(self.root, 0, 0)\n",
"\n",
" def recDisplayTree(self,thisNode,level, childNumber):\n",
" print 'level=' ,level ,' child=',childNumber , ' '\n",
" thisNode.displayNode()\n",
" numItems = thisNode.getNumItems()\n",
" for j in range(numItems+1):\n",
" nextNode = thisNode.getChild(j)\n",
" if(nextNode != None):\n",
" self.recDisplayTree(nextNode, level+1, j)\n",
" else:\n",
" return\n",
"theTree = Tree234()\n",
"theTree.insert(50)\n",
"theTree.insert(40)\n",
"theTree.insert(60)\n",
"theTree.insert(30)\n",
"theTree.insert(70)\n",
"while(True):\n",
" print 'Enter first letter of show, '\n",
" print 'insert, find, or display: ',\n",
" choice = raw_input()\n",
" if choice == 's':\n",
" theTree.displayTree()\n",
" elif choice == 'i':\n",
" print 'Enter value to insert: '\n",
" value = int(raw_input())\n",
" theTree.insert(value)\n",
" elif choice == 'f':\n",
" print 'Enter value to find: ',\n",
" value = int(raw_input())\n",
" found = theTree.find(value)\n",
" if(found != -1):\n",
" print 'Found: ', value\n",
" else:\n",
" print 'Could not find', value \n",
" else:\n",
" print 'Invalid entry'\n"
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