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413 lines (365 loc) · 10.7 KB
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package tree;
import java.util.*;
/**
* 树的基本操作类
*/
public class TreeTools {
/**
* 树中节点的个数
* @param root
* @param <T>
* @return int
*/
public static <T> int getTreeNum(TreeNode<T> root){
if (root==null){
return 0;
}
return getTreeNum(root.leftChild)+getTreeNum(root.rightChild)+1;
}
/**
* 数的深度
* @param root
* @param <T>
* @return int
*/
public static <T> int getTreeDepth(TreeNode<T> root){
if (root == null){
return 0;
}
int leftDepth = getTreeDepth(root.leftChild)+1;
int rightDepth = getTreeDepth(root.rightChild)+1;
return Math.max(leftDepth,rightDepth);
}
/**
* 先序遍历
* @param root
* @param <T>
*/
public static <T> void preOrderTravel(TreeNode<T> root){
if(root==null){
return ;
}
visitNode(root);
preOrderTravel(root.leftChild);
preOrderTravel(root.rightChild);
}
/**
* 中序遍历
* @param root
* @param <T>
*/
public static <T> void midOrderTravel(TreeNode<T> root) {
if (root == null) {
return;
}
midOrderTravel(root.leftChild);
visitNode(root);
midOrderTravel(root.rightChild);
}
/**
* 后续遍历
* @param root
* @param <T>
*/
public static <T> void backOrderTravel(TreeNode<T> root) {
if (root == null) {
return;
}
backOrderTravel(root.leftChild);
backOrderTravel(root.rightChild);
visitNode(root);
}
/**
* visitNode 访问Node节点
* @param node
* @param <T>
*/
public static <T> void visitNode(TreeNode<T> node){
System.out.print(node.value+"\t");
}
/**
* 分层遍历数，层次遍历
* @param root
* @param <T>
*/
public static <T> void levelTravel(TreeNode<T> root){
Queue<TreeNode<T>> q = new LinkedList<>();
q.offer(root);
while(!q.isEmpty()){
TreeNode<T> temp = q.poll();
visitNode(temp);
if(temp.leftChild!=null){
q.offer(temp.leftChild);
}
if(temp.rightChild!=null){
q.offer(temp.rightChild);
}
}
}
/**
* 获得k层的节点数
* @param root 数的根节点
* @param k 树的第多少层
* @param <T>
* @return k层的节点数
*/
public static <T> int getNumForKLevel(TreeNode<T> root,int k ){
if(root==null||k<1){
return 0;
}
if(k==1){
return 1;
}
int leftNum = getNumForKLevel(root.leftChild,k-1);
int rightNum = getNumForKLevel(root.rightChild,k-1);
return leftNum+rightNum;
}
/**
* 求二叉树中叶子节点的数目
* @param root
* @param <T>
* @return
*/
public static <T> int getLeafNum(TreeNode<T> root){
if(root==null){
return 0;
}
if(root.rightChild==null&&root.leftChild==null){
return 1;
}
int leftNum = getLeafNum(root.leftChild);
int rightNum = getLeafNum(root.rightChild);
return leftNum+rightNum;
}
/**
* 交换根节点的左右子树
* @param root
* @param <T>
* @return
*/
public static <T> TreeNode<T> exchange(TreeNode<T> root){
if(root == null)
return null;
TreeNode<T> left = exchange( root.leftChild);
TreeNode<T> right = exchange(root.rightChild);
root.leftChild = right;
root.rightChild = left;
return root;
}
/**
* 查看node是否是root的子节点
* @param root
* @param node
* @param <T>
* @return
*/
public static <T> boolean nodeIsChild(TreeNode<T> root,TreeNode<T> node){
if(root==null||node==null){
return false;
}
if(root==node){
return true;
}
boolean isFind = nodeIsChild(root.leftChild,node);
if(!isFind){
isFind = nodeIsChild(root.rightChild,node);
}
return isFind;
}
/**
* findAllFatherNode: 返回两个节点lnode和rnode的以root为根节点的公共父节点
* @param root
* @param lNode
* @param rNode
* @param <T>
* @return
*/
public static <T> TreeNode<T> findAllFatherNode(TreeNode<T> root,TreeNode<T> lNode,TreeNode<T> rNode){
if(lNode == root||rNode==root){
return root;
}
if(root == null||lNode==null||rNode==null){
return null;
}
if(nodeIsChild(root.leftChild,lNode)){
if(nodeIsChild(root.rightChild,rNode)){
return root;
}else{
return findAllFatherNode(root.leftChild,lNode,rNode);
}
}else{
if(nodeIsChild(root.rightChild,rNode)){
return root;
}else {
return findAllFatherNode(root.rightChild,lNode,rNode);
}
}
}
/**
* 根据树的先序与中序序列重建树
* @param pre 先序遍历序列
* @param mid 中序遍历序列
* @param <T>
* @return
*/
public static <T> TreeNode<T> getTreeFromPreAndMid(List<T> pre,List<T> mid){
if(pre==null||mid==null||pre.size()==0||mid.size()==0){
return null;
}
if(pre.size()==1){
return new TreeNode<T>(pre.get(0));
}
TreeNode<T> root = new TreeNode<>(pre.get(0));
//找出根节点在中序中的位置
int index = 0;
while(!root.value.equals(mid.get(index))) index++;
//构建左子树的前序与中序
List<T> preLeft = new ArrayList<>();
List<T> midLeft = new ArrayList<>();
for(int i=1;i<=index;i++){
preLeft.add(pre.get(i));
}
for(int i=0;i<index;i++){
midLeft.add(mid.get(i));
}
//重建左子树
root.leftChild = getTreeFromPreAndMid(preLeft,midLeft);
//右子树的前序与中序
List<T> preRight = new ArrayList<>();
List<T> midRight = new ArrayList<>();
for(int i =index+1;i<pre.size();i++){
preRight.add(pre.get(i));
}
for(int i = index+1;i<mid.size();i++){
midRight.add(mid.get(i));
}
root.rightChild = getTreeFromPreAndMid(preRight,midRight);
return root;
}
/**
* 比较两个树是否完全相等
* @param node1
* @param node2
* @param <T>
* @return
*/
public static <T> boolean equals(TreeNode<T> node1,TreeNode<T> node2){
if (node1==null&&node2==null){
return true;
}else if (node1==null||node2==null){
return false;
}
boolean isEqual = node1.value.equals(node2.value);
boolean isLeftEqual = equals(node1.leftChild,node2.leftChild);
boolean isRightEqual = equals(node1.rightChild,node2.rightChild);
return isEqual&&isLeftEqual&&isRightEqual;
}
/**
* 非递归的先序遍历
* @param root
* @param <T>
*/
public static <T> void preOrderTravelNoRecursion(TreeNode<T> root){
if (root==null)
return;
Stack<TreeNode<T>> stack = new Stack<>();
TreeNode<T> p = root;
while (!stack.empty()||p!=null){
while (p!=null){
visitNode(p);
stack.push(p);
p = p.leftChild;
}
if(!stack.empty()){
p = stack.pop();
p = p.rightChild;
}
}
}
/**
* 非递归中序遍历
* @param root
* @param <T>
*/
public static <T> void midOrderTravelNoRecursion(TreeNode<T> root){
if (root==null){
return;
}
Stack<TreeNode<T>> stack = new Stack<>();
TreeNode<T> p =root;
while (!stack.empty()||p!=null){
while (p!=null){
stack.push(p);
p = p.leftChild;
}
if(!stack.empty()){
p = stack.pop();
visitNode(p);
p = p.rightChild;
}
}
}
/**
* 非递归后续遍历
* @param root
* @param <T>
*/
public static <T> void BackOrderTravelNoRecursion(TreeNode<T> root){
if (root==null){
return;
}
Stack<TreeNode<T>> stack = new Stack<>();
TreeNode<T> pre =null;
TreeNode<T> current;
stack.push(root);
while(!stack.empty()){
current = stack.peek();
if((current.leftChild==null && current.rightChild==null)//当前节点是叶子节点，可以直接访问
||(pre!=null&&(pre==current.leftChild||pre==current.rightChild)//当前一个节点不为空并且是当前节点的左孩子或者右孩子，当是左孩子代表右孩子为空，当是又孩子表示左右都不为空，且已经访问过
)){
visitNode(current);
stack.pop();
pre = current;
}else{
if(current.rightChild!=null){
////先压栈右节点再压栈左节点 这样出栈时是先左后右
stack.push(current.rightChild);
}
if(current.leftChild!=null){
stack.push(current.leftChild);
}
}
}
}
public static TreeNode<Character> CreateBinTreeByArray(char[] array){
int currLevel = 1;
int currLevelBegin = 0,parentLevelBegin = 0;
TreeNode<Character>[] nodeArray = new TreeNode[array.length];
while (currLevelBegin<array.length){
int levelNumber = (int) Math.pow(2,currLevel-1);
int parentStep = 0;
for(int step=0;step<levelNumber;step++){
int index = currLevelBegin+step;
if(index>=array.length) break;
TreeNode<Character> node = null;
if(array[index]!='#'){
node = new TreeNode<>(array[index]);
nodeArray[index] = node;
}
if(currLevelBegin>0){
TreeNode parentNode = nodeArray[parentLevelBegin+parentStep];
if(step%2==0){
parentNode.leftChild = node;
}else{
parentNode.rightChild = node;
parentStep++;
}
}
}
parentLevelBegin = currLevelBegin;
currLevelBegin+=levelNumber;
currLevel++;
}
return nodeArray[0];
}
}