[移动开发]Android中Tree的使用

Android中Tree的使用：

Tree的简单实例：

01.创建Tree

//创建二叉树数据结构：节点值、左节点、右节点
data class TreeNode(var leftNode: TreeNode? = null,
                    var value: Int? = null,
                    var rightNode: TreeNode? = null) {
    fun frontShow() {
        leftNode?.frontShow()
        rightNode?.frontShow()
    }

    fun midShow() {
        leftNode?.midShow()
        rightNode?.midShow()
    }

    fun afterShow() {
        leftNode?.afterShow()
        rightNode?.afterShow()
    }
}

//创建二叉树对象
data class BinaryTree(var rootNode: TreeNode){
    fun frontShow() {
        rootNode.frontShow()
    }

    fun midShow() {
        rootNode.midShow()
    }

    fun afterShow() {
        rootNode.afterShow()
    }
}

02.显示二叉树

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        //创建左右节点
        var leftNode = TreeNode(TreeNode(value = 4), 2, TreeNode(value = 5))
        var rightNode = TreeNode(TreeNode(value = 6), 3, TreeNode(value = 7))
        //创建根节点，添加左右节点
        var rootNode = TreeNode(leftNode = leftNode, value = 1, rightNode = rightNode)
        //创建二叉树对象
        var tree = BinaryTree(rootNode = rootNode)

        //二叉树的遍历
        tree.frontShow()
        println("tree==$tree")

        tree.midShow()
        println("tree==$tree")

        tree.afterShow()
        println("tree==$tree")
    }
}

Tree的拓展实例：

01.二叉树的遍历

class BinaryTree {
    var root: TreeNode? = null

    //添加节点
    fun insert(value: Int) {
        //创建一个新的节点
        val newNode = TreeNode(value = value)
        when(root) {
            null -> root = newNode
            else -> {
                var currentNode: TreeNode? = root
                var parentNode: TreeNode
                while (true) {
                    parentNode = currentNode!!
                    when {
                        //新的节点
                        newNode.value!! > currentNode.value!! -> {
                            currentNode = currentNode.rightNode
                            if(currentNode == null) {
                                parentNode.rightNode = newNode
                                return
                            }
                        }
                        else -> {
                            currentNode = currentNode.leftNode
                            if(currentNode == null) {
                                parentNode.leftNode = newNode
                                return
                            }
                        }
                    }
                }
            }
        }
    }

    //深度遍历
    fun inOrderDepth(treeNode: TreeNode?) {
        if(treeNode != null) {
            Log.i("前序遍历", "前序遍历：${treeNode.value.toString()}")
            inOrderDepth(treeNode.leftNode)
            Log.i("中序遍历","中序遍历：${treeNode.value.toString()}")
            inOrderDepth(treeNode.rightNode)
            Log.i("后序遍历", "后序遍历：${treeNode}")
        }
    }

    //广度遍历
    fun inOrderWidth(treeNode: TreeNode?) {
        if(treeNode == null) return
        val nodelist = ArrayList<TreeNode>()
        nodelist.add(treeNode)
        while (nodelist.size > 0) {
            val rnode = nodelist[0]
            nodelist.remove(rnode)
            Log.i("广度遍历", "广度遍历：${rnode.value.toString()}")
            rnode.leftNode?.let { nodelist.add(it) }
            rnode.rightNode?.let { nodelist.add(it) }
        }
    }
}

02.创建二叉树

        binaryTree = BinaryTree()
        binaryTree?.insert(10)
        binaryTree?.insert(3)
        binaryTree?.insert(5)
        binaryTree?.insert(6)
        binaryTree?.insert(7)
        Log.i("遍历", "binaryTree==$binaryTree")
        binaryTree?.inOrderDepth(binaryTree!!.root)