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recursived deletion binary tree

This commit is contained in:
Marcos 2017-12-16 12:33:50 +01:00
parent 9ead70be1b
commit 7acbc7902d
1 changed files with 32 additions and 87 deletions
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119
core-java/src/main/java/com/baeldung/tree/BinaryTree.java
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@ -58,89 +58,51 @@ public class BinaryTree {
} }
public void delete(int value) { public void delete(int value) {
deleteRecursive(root, value);
NodeVO nodeToDeleteVO = findNodeToDelete(root, root, false, value);
if (nodeToDeleteVO == null) {
return;
}
// Case 1: no children
if (nodeToDeleteVO.node.left == null && nodeToDeleteVO.node.right == null) {
if (nodeToDeleteVO.node == root) {
root = null;
} else if (nodeToDeleteVO.isLeftChild) {
nodeToDeleteVO.parent.left = null;
} else {
nodeToDeleteVO.parent.right = null;
}
}
// Case 2: only 1 child
else if (nodeToDeleteVO.node.right == null) {
if (nodeToDeleteVO.node == root) {
root = nodeToDeleteVO.node.left;
} else if (nodeToDeleteVO.isLeftChild) {
nodeToDeleteVO.parent.left = nodeToDeleteVO.node.left;
} else {
nodeToDeleteVO.parent.right = nodeToDeleteVO.node.left;
}
} else if (nodeToDeleteVO.node.left == null) {
if (nodeToDeleteVO.node == root) {
root = nodeToDeleteVO.node.right;
} else if (nodeToDeleteVO.isLeftChild) {
nodeToDeleteVO.parent.left = nodeToDeleteVO.node.right;
} else {
nodeToDeleteVO.parent.right = nodeToDeleteVO.node.right;
}
}
// Case 3: 2 children
else if (nodeToDeleteVO.node.left != null && nodeToDeleteVO.node.right != null) {
Node replacement = findReplacement(nodeToDeleteVO.node);
if (nodeToDeleteVO.node == root) {
root = replacement;
} else if (nodeToDeleteVO.isLeftChild) {
nodeToDeleteVO.parent.left = replacement;
} else {
nodeToDeleteVO.parent.right = replacement;
}
}
} }
private NodeVO findNodeToDelete(Node current, Node parent, boolean isLeftChild, int value) { private Node deleteRecursive(Node current, int value) {
if (current == null) { if (current == null) {
return null; return null;
} else if (value == current.value) { }
return new NodeVO(current, parent, isLeftChild);
if (value == current.value) {
// Case 1: no children
if (current.left == null && current.right == null) {
return null;
}
// Case 2: only 1 child
if (current.right == null) {
return current.left;
}
if (current.left == null) {
return current.right;
}
// Case 3: 2 children
int smallestValue = findSmallestNode(current.right);
current.value = smallestValue;
current.right = deleteRecursive(current.right, smallestValue);
return current;
} else if (value < current.value) { } else if (value < current.value) {
return findNodeToDelete(current.left, current, true, value); current.left = deleteRecursive(current.left, value);
return current;
} else { } else {
return findNodeToDelete(current.right, current, false, value); current.right = deleteRecursive(current.right, value);
return current;
} }
} }
private Node findReplacement(Node nodeToDelete) { private int findSmallestNode(Node root) {
NodeVO replacementNodeVO = findSmallestNode(nodeToDelete, nodeToDelete);
if (replacementNodeVO.node != nodeToDelete.right) {
replacementNodeVO.parent.left = replacementNodeVO.node.right;
replacementNodeVO.node.right = nodeToDelete.right;
}
replacementNodeVO.node.left = nodeToDelete.left;
return replacementNodeVO.node;
}
private NodeVO findSmallestNode(Node root, Node parent) {
if (root.left == null) { if (root.left == null) {
return new NodeVO(root, parent); return root.value;
} }
return findSmallestNode(root.left, root); return findSmallestNode(root.left);
} }
public void traverseInOrder(Node node) { public void traverseInOrder(Node node) {
@ -188,23 +150,6 @@ public class BinaryTree {
} }
} }
class NodeVO {
Node node;
Node parent;
boolean isLeftChild;
NodeVO(Node node, Node parent) {
this.node = node;
this.parent = parent;
}
NodeVO(Node node, Node parent, boolean isLeftChild) {
this.node = node;
this.parent = parent;
this.isLeftChild = isLeftChild;
}
}
class Node { class Node {
int value; int value;
Node left; Node left;