参照着《数据结构java语言描述》的伪码，自己实现的方法细节，最复杂的一个方法是remove()
package DataStructure.Tree;
public class IntTreeBag implements Cloneable {
private Node root;
public class Node {
Node(int element, Node left, Node right) {
this.element = element;
this.left = left;
this.right = right;
}
public Node getLeft() {
return left;
}
public Node getRight() {
return right;
}
private int element;
private Node left;
private Node right;
@Override
public String toString() {
return String.valueOf(element);
}
}
public IntTreeBag() {
this(0);
}
public IntTreeBag(int rootValue) {
root = new Node(rootValue, null, null);
}
public int size() {
return size(root);
}
private int size(Node node) {
if (node == null) {
return 0;
} else {
return 1 + size(node.left) + size(node.right);
}
}
public Node getRoot() {
return root;
}
public void add(int target) {
boolean done = false;
Node cursor = root;
while (!done) {
if (target < cursor.element) {
if (cursor.left == null) {
cursor.left = new Node(target, null, null);
done = true;
} else {
cursor = cursor.left;
}
} else if (target > cursor.element) {
if (cursor.right == null) {
cursor.right = new Node(target, null, null);
done = true;
} else {
cursor = cursor.right;
}
} else {//target==cursor.element
//查找二叉树还是暂时不做有相同结点的处理。
// if (cursor.left == null) {
// cursor.left = new Node(target, null, null);
// done = true;
// } else {
// cursor = cursor.left;
// }
done=true;
}
}
}
/**
* 删除值为target的目标结点，巧妙地记录下游标结点的父结点，并判断
* 当前游标在左子树还是右子树，然后操作游标结点的父结点即可容易删除目标。
*
* 删除操作将目标分成5种类型来操作，分别是：
* 目标是根节点，目标左右结点为空，目标仅左结点为空，
* 目标仅右结点为空，目标左右结点非空
*
* @param target 目标
* @return 如果成功删除返回true，否则返回false
*/
public boolean remove(int target) {
if (isEmpty()) {
return true;
}
Node parentOfCursor = null;//cursor的父结点
Node cursor = root;
boolean inLeft=false;//记录cursor是在左结点还是在右结点
boolean done = false;
while (!done) {
if (cursor==null){//没有找到target
return false;
}
if (target < cursor.element) {
parentOfCursor = cursor;
cursor = cursor.left;
inLeft=true;
} else if (target > cursor.element) {
parentOfCursor = cursor;
cursor = cursor.right;
inLeft=false;
} else {//target == cursor.element
if (cursor == root) {//cursor就是根结点, cursor没有向下搜索过, inLeft和parentOfCursor都还是初始值
if (cursor.left == null) {
root = root.right;
done=true;
} else {//root.left!=null
if (root.left.right == null) {
root.left.right = root.right;
root = root.left;
done=true;
} else {
root.element = getRightMostNode(root.left).element;
removeRightMostNode(root.left);
done=true;
}
}
} else if (cursor.left == null && cursor.right == null) {//左右结点都为空
if (inLeft){
parentOfCursor.left=null;
done=true;
}else {
parentOfCursor.right=null;
done=true;
}
}else if (cursor.left == null){//左结点为空，右结点不为空
if (inLeft){
parentOfCursor.left=cursor.right;
done=true;
}else {
parentOfCursor.right=cursor.right;
done=true;
}
}else if (cursor.right == null){//右结点为空，左结点不为空
if (inLeft){
parentOfCursor.left=cursor.left;
done=true;
}else {
parentOfCursor.right=cursor.left;
done=true;
}
}else {//左右两个子结点都不为空
if (cursor.left.right==null){
cursor.left.right=cursor.right;
if (inLeft){
parentOfCursor.left=cursor.left;
done=true;
}else {
parentOfCursor.right=cursor.left;
done=true;
}
}else {
cursor.element=getRightMostNode(cursor.left).element;
removeRightMostNode(cursor.left);
done=true;
}
}
}
}
return true;//能跳出while循环就是done=true，成功删除了。
}
public boolean isEmpty() {
return root == null;
}
/**
* remove the most left node of the rootNode
*
* @param rootNode .
* @return return true if remove target. return
* false if the left of rootNode is null.
*/
public boolean removeLeftMostNode(Node rootNode) {
Node c = rootNode;
Node parentOfc = null;
while (c.left != null) {
parentOfc = c;
c = c.left;
}
if (parentOfc != null) {//rootNode.left!=null
parentOfc.left = null;
return true;
} else {
//rootNode.left==null.
return false;
}
}
public boolean removeRightMostNode(Node rootNode) {
Node c = rootNode;
Node parentOfc = null;
while (c.left != null) {
parentOfc = c;
c = c.right;
}
if (parentOfc != null) {
parentOfc.right = null;
return true;
} else {
return false;
}
}
public Node getLeftMostNode(Node rootNode) {
Node cursor = rootNode;
while (cursor.left != null) {
cursor = cursor.left;
}
return cursor;
}
public Node getRightMostNode(Node rootNode) {
Node cursor = rootNode;
while (cursor.right != null) {
cursor = cursor.right;
}
return cursor;
}
public int countOccurences(int target) {
int count = 0;
Node cursor = root;
while (cursor != null) {
if (target < cursor.element) {
cursor = cursor.left;
} else if (target > cursor.element) {
cursor = cursor.right;
} else if (target == cursor.element) {
cursor = cursor.left;
count++;
}
}
return count;
}
@Override
protected Object clone() throws CloneNotSupportedException {
super.clone();
return treeCopy(root);
}
//深度拷贝一个树，返回拷贝的全新的树的根节点。
private Node treeCopy(Node node) {
Node left, right;
if (node == null) {
return null;
} else {
left = treeCopy(node.left);
right = treeCopy(node.right);
return new Node(node.element, left, right);
}
}
/**
* 先序遍历打印
* @param node 根节点
*/
public void preorderPrint(Node node){
if (node!=null){
System.out.println(node.element);
if (node.left!=null){
preorderPrint(node.left);
}
if (node.right!=null){
preorderPrint(node.right);
}
}
}
/**
* 添加一棵树，传入根结点即可
* 因为内部调用了add()，因此会过滤掉相同element的结点。
* @param node root of the tree to be added
*/
public void addAll(Node node){
if (node!=null){
this.add(node.element);
if (node.left!=null){
addAll(node.left);
}
if (node.right!=null){
addAll(node.right);
}
}
}
public void addMany(int...elements){
for (int i=0;i<elements.length;i++){
add(elements[i]);
}
}
/**
* 按从小到大的顺序打印，其实是中序遍历
* @param node 根节点
*/
public void printInSequence(Node node){
if (node!=null){
if (node.left!=null){
printInSequence(node.left);
}
System.out.print(node.element+" ");
if (node.right!=null){
printInSequence(node.right);
}
}
}
/**
* 倒序打印，即从大到小打印树，也是中序遍历，
* 不过是先右结点，根节点，再左结点
* @param node
*/
public void printInReverseSequence(Node node){
if (node!=null){
if (node.right!=null){
printInReverseSequence(node.right);
}
System.out.print(node.element+" ");
if (node.left!=null){
printInReverseSequence(node.left);
}
}
}
}
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