This is my first ever trial at implementing the BST, and I am unable to get it done. Please help
The problem is that When I delete the node if the node is in the right subtree from the root or if its a right child in the left subtree, then it works fine. But if the node is in the left subtree from root and its any left child, then it does not get deleted.
Can someone show me what mistake am I doing??
the markedNode here gets allocated to the parent node of the node to be deleted.
the minValueNode here gets allocated to a node whose left value child is the smallest value and it will be used to replace the value to be deleted.
package DataStructures;
class Node {
int value;
Node rightNode;
Node leftNode;
}
class BST {
Node rootOfTree = null;
public void insertintoBST(int value) {
Node markedNode = rootOfTree;
if (rootOfTree == null) {
Node newNode = new Node();
newNode.value = value;
rootOfTree = newNode;
newNode.rightNode = null;
newNode.leftNode = null;
} else {
while (true) {
if (value >= markedNode.value) {
if (markedNode.rightNode != null) {
markedNode = markedNode.rightNode;
} else {
Node newNode = new Node();
newNode.value = value;
markedNode.rightNode = newNode;
newNode.rightNode = null;
newNode.leftNode = null;
break;
}
}
if (value < markedNode.value) {
if (markedNode.leftNode != null) {
markedNode = markedNode.leftNode;
} else {
Node newNode = new Node();
newNode.value = value;
markedNode.leftNode = newNode;
newNode.rightNode = null;
newNode.leftNode = null;
break;
}
}
}
}
}
public void searchBST(int value) {
Node markedNode = rootOfTree;
if (rootOfTree == null) {
System.out.println("Element Not Found");
} else {
while (true) {
if (value > markedNode.value) {
if (markedNode.rightNode != null) {
markedNode = markedNode.rightNode;
} else {
System.out.println("Element Not Found");
break;
}
}
if (value < markedNode.value) {
if (markedNode.leftNode != null) {
markedNode = markedNode.leftNode;
} else {
System.out.println("Element Not Found");
break;
}
}
if (value == markedNode.value) {
System.out.println("Element Found");
break;
}
}
}
}
public void deleteFromBST(int value) {
Node markedNode = rootOfTree;
Node minValueNode = null;
if (rootOfTree == null) {
System.out.println("Element Not Found");
return;
}
if (rootOfTree.value == value) {
if (rootOfTree.leftNode == null && rootOfTree.rightNode == null) {
rootOfTree = null;
return;
} else if (rootOfTree.leftNode == null
^ rootOfTree.rightNode == null) {
if (rootOfTree.rightNode != null) {
rootOfTree = rootOfTree.rightNode;
return;
} else {
rootOfTree = rootOfTree.leftNode;
return;
}
} else {
minValueNode = rootOfTree.rightNode;
if (minValueNode.leftNode == null) {
rootOfTree.rightNode.leftNode = rootOfTree.leftNode;
rootOfTree = rootOfTree.rightNode;
} else {
while (true) {
if (minValueNode.leftNode.leftNode != null) {
minValueNode = minValueNode.leftNode;
} else {
break;
}
}
// Minvalue to the left of minvalue node
rootOfTree.value = minValueNode.leftNode.value;
// The value has been swapped
if (minValueNode.leftNode.leftNode == null
&& minValueNode.leftNode.rightNode == null) {
minValueNode.leftNode = null;
} else {
if (minValueNode.leftNode.leftNode != null) {
minValueNode.leftNode = minValueNode.leftNode.leftNode;
} else {
minValueNode.leftNode = minValueNode.leftNode.rightNode;
}
// Minvalue deleted
}
}
}
} else {
while (true) {
if (value > markedNode.value) {
if (markedNode.rightNode != null) {
if (markedNode.rightNode.value == value) {
break;
} else {
markedNode = markedNode.rightNode;
}
} else {
System.out.println("Element Not Found");
return;
}
}
if (value < markedNode.value) {
if (markedNode.leftNode != null) {
if (markedNode.leftNode.value == value) {
break;
} else {
markedNode = markedNode.leftNode;
}
} else {
System.out.println("Element Not Found");
return;
}
}
}
// Parent of the required element found
// ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
if (markedNode.rightNode != null) {
if (markedNode.rightNode.value == value) {
if (markedNode.rightNode.rightNode == null
&& markedNode.rightNode.leftNode == null) {
markedNode.rightNode = null;
return;
} else if (markedNode.rightNode.rightNode == null
^ markedNode.rightNode.leftNode == null) {
if (markedNode.rightNode.rightNode != null) {
markedNode.rightNode = markedNode.rightNode.rightNode;
return;
} else {
markedNode.rightNode = markedNode.rightNode.leftNode;
return;
}
} else {
if (markedNode.rightNode.value == value) {
minValueNode = markedNode.rightNode.rightNode;
} else {
minValueNode = markedNode.leftNode.rightNode;
}
if (minValueNode.leftNode == null) {
// MinNode has no left value
markedNode.rightNode = minValueNode;
return;
} else {
while (true) {
if (minValueNode.leftNode.leftNode != null) {
minValueNode = minValueNode.leftNode;
} else {
break;
}
}
// Minvalue to the left of minvalue node
if (markedNode.leftNode != null) {
if (markedNode.leftNode.value == value) {
markedNode.leftNode.value = minValueNode.leftNode.value;
}
}
if (markedNode.rightNode != null) {
if (markedNode.rightNode.value == value) {
markedNode.rightNode.value = minValueNode.leftNode.value;
}
}
// MarkedNode exchanged
if (minValueNode.leftNode.leftNode == null
&& minValueNode.leftNode.rightNode == null) {
minValueNode.leftNode = null;
} else {
if (minValueNode.leftNode.leftNode != null) {
minValueNode.leftNode = minValueNode.leftNode.leftNode;
} else {
minValueNode.leftNode = minValueNode.leftNode.rightNode;
}
// Minvalue deleted
}
}
}
// ////////////////////////////////////////////////////////////////////////////////////////////////////////////////
if (markedNode.leftNode != null) {
if (markedNode.leftNode.value == value) {
if (markedNode.leftNode.rightNode == null
&& markedNode.leftNode.leftNode == null) {
markedNode.leftNode = null;
return;
} else if (markedNode.leftNode.rightNode == null
^ markedNode.leftNode.leftNode == null) {
if (markedNode.leftNode.rightNode != null) {
markedNode.leftNode = markedNode.leftNode.rightNode;
return;
} else {
markedNode.leftNode = markedNode.leftNode.leftNode;
return;
}
} else {
if (markedNode.rightNode.value == value) {
minValueNode = markedNode.rightNode.rightNode;
} else {
minValueNode = markedNode.leftNode.rightNode;
}
if (minValueNode.leftNode == null) {
// MinNode has no left value
markedNode.leftNode = minValueNode;
return;
} else {
while (true) {
if (minValueNode.leftNode.leftNode != null) {
minValueNode = minValueNode.leftNode;
} else {
break;
}
}
// Minvalue to the left of minvalue node
if (markedNode.leftNode != null) {
if (markedNode.leftNode.value == value) {
markedNode.leftNode.value = minValueNode.leftNode.value;
}
}
if (markedNode.rightNode != null) {
if (markedNode.rightNode.value == value) {
markedNode.rightNode.value = minValueNode.leftNode.value;
}
}
// MarkedNode exchanged
if (minValueNode.leftNode.leftNode == null
&& minValueNode.leftNode.rightNode == null) {
minValueNode.leftNode = null;
} else {
if (minValueNode.leftNode.leftNode != null) {
minValueNode.leftNode = minValueNode.leftNode.leftNode;
} else {
minValueNode.leftNode = minValueNode.leftNode.rightNode;
}
// Minvalue deleted
}
}
}
}
// ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
}
}
}
}
}
}
public class BSTImplementation {
public static void main(String[] args) {
BST newBst = new BST();
newBst.insertintoBST(19);
newBst.insertintoBST(13);
newBst.insertintoBST(10);
newBst.insertintoBST(20);
newBst.insertintoBST(5);
newBst.insertintoBST(23);
newBst.insertintoBST(28);
newBst.insertintoBST(16);
newBst.insertintoBST(27);
newBst.insertintoBST(9);
newBst.insertintoBST(4);
newBst.insertintoBST(22);
newBst.insertintoBST(17);
newBst.insertintoBST(30);
newBst.insertintoBST(40);
newBst.deleteFromBST(5);
newBst.deleteFromBST(4);
newBst.deleteFromBST(9);
newBst.deleteFromBST(10);
newBst.deleteFromBST(13);
newBst.deleteFromBST(16);
newBst.deleteFromBST(17);
newBst.searchBST(5);
newBst.searchBST(4);
newBst.searchBST(9);
newBst.searchBST(10);
newBst.searchBST(13);
newBst.searchBST(16);
newBst.searchBST(17);
System.out.println();
newBst.deleteFromBST(20);
newBst.deleteFromBST(23);
newBst.deleteFromBST(27);
newBst.deleteFromBST(28);
newBst.deleteFromBST(30);
newBst.deleteFromBST(40);
newBst.searchBST(20);
newBst.searchBST(23);
newBst.searchBST(27);
newBst.searchBST(28);
newBst.searchBST(30);
newBst.searchBST(40);
}
}
