【Java数据结构】实现二叉树及其基本操作

爱被打了一巴掌 2024-04-03 10:24 86阅读 0赞

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BinaryTree.java

import java.util.LinkedList;
    import java.util.Queue;
    
    public class BinaryTree {
    
        static class TreeNode {
            public char val;
            public TreeNode left;//左孩子的引用
            public TreeNode right;//右孩子的引用
    
            public TreeNode(char val) {
                this.val = val;
            }
        }
    
    
        /**
         * 创建一棵二叉树 返回这棵树的根节点
         *
         * @return
         */
        public TreeNode createTree() {
            TreeNode A=new TreeNode('A');
            TreeNode B=new TreeNode('B');
            TreeNode C=new TreeNode('C');
            TreeNode D=new TreeNode('D');
            TreeNode E=new TreeNode('E');
            TreeNode F=new TreeNode('F');
            A.left=B;
            A.right=C;
            C.left=F;
            B.left=D;
            B.right=E;
    
    
            return A;
    
        }
    
        // 前序遍历
        public void preOrder(TreeNode root) {
            if(root==null){
                return;
            }
            System.out.print(root.val+" ");
            preOrder(root.left);
            preOrder(root.right);
    
        }
    
        // 中序遍历
        void inOrder(TreeNode root) {
            if(root==null){
                return;
            }
            inOrder(root.left);
            System.out.print(root.val+" ");
            inOrder(root.right);
        }
    
        // 后序遍历
        void postOrder(TreeNode root) {
            if(root==null){
                return;
            }
            postOrder(root.left);
            postOrder(root.right);
            System.out.print(root.val+" ");
    
        }
    
        public static int nodeSize;
    
        /**
         * 获取树中节点的个数：遍历思路
         */
      public int size(TreeNode root) {
          if(root==null){
              return 0;
          }
          nodeSize++;
          size(root.left);
          size(root.right);
          return nodeSize;
    
        }
    
        /**
         * 获取节点的个数：子问题的思路
         *
         * @param root
         * @return
         */
       public int size2(TreeNode root) {
           if(root==null){
               return 0;
           }
           return size2(root.left)+size2(root.right)+1;
        }
    
    
        /*
         获取叶子节点的个数：遍历思路
         */
        public static int leafSize = 0;
    
        public int getLeafNodeCount1(TreeNode root) {
            if(root==null)return 0;
            if(root.left==null&&root.right==null)
                leafSize++;
            getLeafNodeCount1(root.left);
            getLeafNodeCount1(root.right);
            return leafSize;
        }
    
        /*
         获取叶子节点的个数：子问题
         */
        public int getLeafNodeCount2(TreeNode root) {
            if(root==null)return 0;
            if(root.left==null&&root.right==null)
                return 1;
            return getLeafNodeCount2(root.left)+getLeafNodeCount2(root.right);
    
        }
    
        /*
        获取第K层节点的个数
         */
        public int getKLevelNodeCount(TreeNode root, int k) {
            if(root==null||k<=0)return 0;
            if(k==1)return 1;
    
            return getKLevelNodeCount(root.left,k-1)+getKLevelNodeCount(root.right,k-1);
    
        }
    
        /*
         获取二叉树的高度
    
         */
        public int getHeight(TreeNode root) {
    
            if(root==null)return 0;
    
            return Math.max(getHeight(root.left),getHeight(root.right))+1;
        }
    
    
        // 检测值为value的元素是否存在
        public TreeNode find(TreeNode root, char val) {
            if(root==null)return null;
    
            if(root.val==val)return root;
            if(find(root.left,val)!=null)
                return find(root,val);
            if(find(root.right,val)!=null)
                return find(root.right,val);
    
            return null;
    
        }
    
        //层序遍历
       public void levelOrder(TreeNode root) {
            if(root==null)return;
    
           Queue<TreeNode>qu=new LinkedList<>();
           qu.offer(root);
           while(!qu.isEmpty()){
    
               TreeNode cur=qu.poll();
               System.out.print(cur.val+" ");
    
               if(cur.left!=null)
                   qu.offer(cur.left);
               if(cur.right!=null)
                   qu.offer(cur.right);
    
           }
    
    
        }
    
    
        // 判断一棵树是不是完全二叉树
       public boolean isCompleteTree(TreeNode root) {
           if(root==null)return true;
    
           Queue<TreeNode>qu=new LinkedList<>();
           qu.offer(root);
           while(!qu.isEmpty()){
    
               TreeNode cur=qu.poll();
               if(cur!=null){
                   qu.offer(cur.left);
                   qu.offer(cur.right);
               }else{
                   break;
               }
    
           }
    
           while(!qu.isEmpty()){
               TreeNode pop=qu.poll();
               if(pop!=null)return false;
    
           }
           return true;
        }
    }

Test.java

public class Test {
        public static void main(String[] args) {
            BinaryTree binaryTree=new BinaryTree();
    
            binaryTree.preOrder(binaryTree.createTree());
            System.out.println();
    
            binaryTree.inOrder(binaryTree.createTree());
    
            System.out.println();
            binaryTree.postOrder(binaryTree.createTree());
            System.out.println();
            System.out.println(binaryTree.size(binaryTree.createTree()));
            System.out.println(binaryTree.size2(binaryTree.createTree()));
            System.out.println(binaryTree.getLeafNodeCount1(binaryTree.createTree()));
            System.out.println(binaryTree.getLeafNodeCount2(binaryTree.createTree()));
            System.out.println(binaryTree.getKLevelNodeCount(binaryTree.createTree(), 3));
            System.out.println(binaryTree.getHeight(binaryTree.createTree()));
            System.out.println("=========================");
            binaryTree.levelOrder(binaryTree.createTree());
            System.out.println(binaryTree.isCompleteTree(binaryTree.createTree()));
    
    
        }
    }

测试结果：

![650b99181c82411095ae5d25dacd5537.png][]

[ced485cbb11e458d81a746890b32cf3f.gif]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/03/c2312ac326504f9ab363138ae7a621b9.gif
[Link 1]: https://blog.csdn.net/m0_67995737?type=blog
[Link 2]: https://blog.csdn.net/m0_67995737/category_12000344.html
[Link 3]: https://www.nowcoder.com/link/pc_csdncpt_ylcxx_c
[76ed71c5c00c4340e942a26834e97ddb.jpeg]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/03/70ee607b7758462990ade3c94f1450b4.jpeg
[650b99181c82411095ae5d25dacd5537.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/03/ba177dd7d3864676b0e7778111164c27.png