{"id":16970205,"url":"https://github.com/joyang1/binarytree","last_synced_at":"2025-04-12T00:21:14.326Z","repository":{"id":93784423,"uuid":"82911877","full_name":"joyang1/BinaryTree","owner":"joyang1","description":"二叉树的创建以及三种遍历","archived":false,"fork":false,"pushed_at":"2019-04-20T15:21:04.000Z","size":17,"stargazers_count":5,"open_issues_count":0,"forks_count":2,"subscribers_count":1,"default_branch":"master","last_synced_at":"2025-03-25T20:05:52.447Z","etag":null,"topics":["binary-tree"],"latest_commit_sha":null,"homepage":null,"language":"Java","has_issues":true,"has_wiki":null,"has_pages":null,"mirror_url":null,"source_name":null,"license":null,"status":null,"scm":"git","pull_requests_enabled":true,"icon_url":"https://github.com/joyang1.png","metadata":{"files":{"readme":"README.md","changelog":null,"contributing":null,"funding":null,"license":null,"code_of_conduct":null,"threat_model":null,"audit":null,"citation":null,"codeowners":null,"security":null,"support":null,"governance":null,"roadmap":null,"authors":null,"dei":null,"publiccode":null,"codemeta":null}},"created_at":"2017-02-23T09:45:23.000Z","updated_at":"2023-09-19T03:09:47.000Z","dependencies_parsed_at":"2023-06-15T00:15:28.250Z","dependency_job_id":null,"html_url":"https://github.com/joyang1/BinaryTree","commit_stats":null,"previous_names":[],"tags_count":0,"template":false,"template_full_name":null,"repository_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/joyang1%2FBinaryTree","tags_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/joyang1%2FBinaryTree/tags","releases_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/joyang1%2FBinaryTree/releases","manifests_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/joyang1%2FBinaryTree/manifests","owner_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners/joyang1","download_url":"https://codeload.github.com/joyang1/BinaryTree/tar.gz/refs/heads/master","host":{"name":"GitHub","url":"https://github.com","kind":"github","repositories_count":248498087,"owners_count":21114035,"icon_url":"https://github.com/github.png","version":null,"created_at":"2022-05-30T11:31:42.601Z","updated_at":"2022-07-04T15:15:14.044Z","host_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub","repositories_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories","repository_names_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repository_names","owners_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners"}},"keywords":["binary-tree"],"created_at":"2024-10-14T00:27:40.495Z","updated_at":"2025-04-12T00:21:14.307Z","avatar_url":"https://github.com/joyang1.png","language":"Java","funding_links":[],"categories":[],"sub_categories":[],"readme":"## 二叉树(Binary Tree)定义:\n二叉树是每个节点最多有两个子树的树结构。通常子树被称作“左子树”（left subtree）和“右子树”（right subtree）。二叉树常被用于实现二叉查找树和二叉堆。\n\n二叉树的每个结点至多只有二棵子树(不存在度大于2的结点)，二叉树的子树有左右之分，次序不能颠倒。二叉树的第i层至多有2^{i-1}个结点；深度为k的二叉树至多有2^k-1个结点；对任何一棵二叉树T，如果其终端结点数为n_0，度为2的结点数为n_2，则n_0=n_2+1。\n\n一棵深度为k，且有2^k-1个节点称之为满二叉树；深度为k，有n个节点的二叉树，当且仅当其每一个节点都与深度为k的满二叉树中，序号为1至n的节点对应时，称之为完全二叉树。\n\n## Create Binary Tree Using Java\n\n```sh\n//arrs为放入到树节点的数据，demo中将int类型的数据置入节点中\npublic List\u003cTreeNode\u003e initTree(int[] arrs) {\n\t\tList\u003cTreeNode\u003e nodes = new ArrayList\u003cTreeNode\u003e();\n\t\tfor (int data : arrs) {\n\t\t\tnodes.add(new TreeNode(data));\n\t\t}\n\t\t//此处每个父节点的index \u003c (arrs.length / 2 - 1)是确保每个父节点的左右子节点都存在 \n\t\tfor (int parentIndex = 0; parentIndex \u003c arrs.length / 2 - 1; parentIndex++) {\n\t\t\tnodes.get(parentIndex).leftNode = nodes.get(parentIndex * 2 + 1);\n\t\t\tnodes.get(parentIndex).rightNode = nodes.get(parentIndex * 2 + 2); \n\t\t}\n\t\t//(arrs.length / 2 - 1)最后一个父节点，通过二叉树的定义可知\t\t\n                int lastParentIndex = arrs.length / 2 - 1;\n\t\tnodes.get(lastParentIndex).leftNode = nodes.get(lastParentIndex * 2 + 1);\n\t\t//arrs.length % 2 != 0,作为判断最后一个父节点的右子节点是否存在的判断条件\t\t\n                if(arrs.length % 2 != 0){\n\t\t\tnodes.get(lastParentIndex).rightNode = nodes.get(lastParentIndex * 2 + 2);\n\t\t}\n\t\treturn nodes;\n}\n```\n上述方法中提到的TreeNode对象在code(src.test.TreeNode)中可以查看。\n\n## 三种遍历方式\n\n(1). 先序遍历\u003cbr/\u003e\n(2). 中序遍历\u003cbr/\u003e\n(3). 后序遍历\u003cbr/\u003e\n三种遍历方式，也就是遍历的顺序不一样。\u003cbr/\u003e\n先序遍历: \"根左右\"，遍历的顺序: 根节点-\u003e左节点-\u003e右节点。\u003cbr/\u003e\n中序遍历: \"左根右\"，遍历的顺序: 左节点-\u003e根节点-\u003e右节点。\u003cbr/\u003e\n后序遍历: \"左右根\"，遍历的顺序: 左节点-\u003e右节点-\u003e根节点。\u003cbr/\u003e\n\n## 先序遍历\n\n使用递归\n```sh\n\t/*\n\t * 先序遍历二叉树： 根左右\n\t * \n\t * @param node\n\t *       遍历的节点\n\t * */\n\tpublic void preOrderTraverse(TreeNode node){\n\t\tif(node == null)\n\t\t\treturn;\n\t\tSystem.out.print(node.data + \" \"); //第一次进来是rootNode\n\t\tpreOrderTraverse(node.leftNode);  //递归输出左节点\t\t\n                preOrderTraverse(node.rightNode); //递归输出右节点\n\t}\n```\n\n使用循环\n```sh\n\t/*\n\t * 先序遍历二叉树： 根左右\n\t * \n\t * 使用循环\n\t * \n\t * @param node\n\t *       遍历的节点\n\t * */\n\tpublic void preOrderTraverseByWhile(TreeNode node){\n\t\tLinkedList\u003cTreeNode\u003e stack = new LinkedList\u003cTreeNode\u003e();\n\t\tstack.push(node);\n\t\tTreeNode currentNode;\n\t\twhile (!stack.isEmpty()) {\n\t\t\tcurrentNode = stack.pop();\n\t\t\tSystem.out.print(currentNode.data + \" \");\n\t\t\tif(currentNode.rightNode != null){\n\t\t\t\tstack.push(currentNode.rightNode);\n\t\t\t}\n\t\t\tif (currentNode.leftNode != null) {\n\t\t\t\tstack.push(currentNode.leftNode);\n\t\t\t}\n\t\t}\n\t}\n```\n\n## 中序遍历\n\n使用递归\n```sh\n\t/*\n\t * 中序遍历二叉树： 左根右\n\t * \n\t * @param node\n\t *       遍历的节点\n\t * */\n\tpublic void inOrderTraverse(TreeNode node){\n\t\tif(node == null)\n\t\t\treturn;\n\t\tinOrderTraverse(node.leftNode); //递归输出左节点\n\t\tSystem.out.print(node.data + \" \"); \n\t\tinOrderTraverse(node.rightNode); //递归输出右节点\n\t}\n```\n\n使用循环\n```sh\n\t/*\n\t * 中序遍历二叉树： 左根右\n\t * \n\t * 使用循环\n\t * \n\t * @param node\n\t *       遍历的节点\n\t * */\n\tpublic void inOrderTraverseByWhile(TreeNode node){\n\t\tLinkedList\u003cTreeNode\u003e stack = new LinkedList\u003cTreeNode\u003e();\n\t\tTreeNode currentNode = node;\n\t\twhile (currentNode != null || !stack.isEmpty()) {\n\t\t\twhile(currentNode != null){\n\t\t\t\tstack.push(currentNode);\n\t\t\t\tcurrentNode = currentNode.leftNode;\n\t\t\t}\n\t\t\tif(!stack.isEmpty()){\n\t\t\t\tcurrentNode = stack.pop();\n\t\t\t\tSystem.out.print(currentNode.data + \"\");\n\t\t\t\tcurrentNode = currentNode.rightNode;\n\t\t\t}\n\t\t}\n\t}\n```\n\n## 后序遍历\n\n使用递归\n```sh\n\t/*\n\t * 后序遍历二叉树： 左右根\n\t * \n\t * @param node\n\t *       遍历的节点\n\t * */\n\tpublic void afterOrderTraverse(TreeNode node){\n\t\tif(node == null)\n\t\t\treturn;\n\t\tafterOrderTraverse(node.leftNode);//递归输出左节点\n\t\tafterOrderTraverse(node.rightNode);//递归输出右节点\n\t\tSystem.out.print(node.data + \" \");\n\t}\n```\n\n使用循环\n```sh\n\t/*\n\t * 后序遍历二叉树： 左右根\n\t * \n\t *  使用循环\n\t * \n\t * @param node\n\t *       遍历的节点\n\t * */\n\tpublic void afterOrderTraverseByWhile(TreeNode node){\n\t\tLinkedList\u003cTreeNode\u003e stack = new LinkedList\u003cTreeNode\u003e();\n\t\tTreeNode rightNode = null;\n\t\tTreeNode currentNode = node;\n\t\twhile (currentNode != null || !stack.isEmpty()) {\n\t\t\twhile(currentNode != null){\n\t\t\t\tstack.push(currentNode);\n\t\t\t\tcurrentNode = currentNode.leftNode;\n\t\t\t}\n\t\t\tcurrentNode = stack.pop();\n\t\t\t//当上一个访问的结点是右孩子或者当前结点没有右孩子则访问当前结点\n\t\t\twhile(currentNode != null \u0026\u0026 (currentNode.rightNode == null || currentNode.rightNode == rightNode)){\n\t\t\t\tSystem.out.print(currentNode.data + \" \");\n\t\t\t\trightNode = currentNode;\n\t\t\t\tif(stack.isEmpty()){\n\t\t\t\t\treturn;\n\t\t\t\t}\n\t\t\t\tcurrentNode = stack.pop();\n\t\t\t}\n\t\t\tstack.push(currentNode);\n\t\t\tcurrentNode = currentNode.rightNode;\n\t\t}\n\t}\n```\n\n## how to run code\n1. 将代码clone到本地，使用eclipse导入代码，导入的时候项目的类型选择\"git project\"。\n2. 找到src/test/RunTest.java，右键 run as java appalication.\n\ndemo中设置的二叉树的结构为:\u003cbr /\u003e\n![](http://blog.tommyyang.cn/img/binary-tree.png)\u003cbr /\u003e\nRunTest结果如下:\u003cbr /\u003e\n\n![](http://blog.tommyyang.cn/img/binarytree-xunhuanresult.png)\n","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fjoyang1%2Fbinarytree","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Fjoyang1%2Fbinarytree","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fjoyang1%2Fbinarytree/lists"}