數據結構之二叉樹（java版）

時間 2019-11-10

原文原文鏈接

二叉樹是數據結構中很重要的結構類型，學習數據結構也是深刻學習編程的必由之路，這裏咱們簡單介紹下我對於二叉樹的理解，水平有限，若有錯誤還請不吝賜教。java

首先照例定義一個二叉樹的節點類

class Node {
     private int value;//二叉樹的值
     private Node leftChild;//左孩子節點
     private Node rightChild;//右孩子節點

     public Node(int value, Node leftChild, Node rightChild) {
         this.value = value;
         this.leftChild = leftChild;
         this.rightChild = rightChild;
     }
}

插入節點

本次用到的二叉樹是順序二叉樹，即判斷當前插入的節點值與二叉樹中父節點比較，若是value值大於父節點，插入父節點的右子樹種，反之，插入左子樹種，以此類推，直到找到相應的字節點插入。node

public void insert(int value) {
        if (parent == null) {//父節點爲空判斷
            Node node = new Node(value, null, null);
            parent = node;
            length++;
        } else {
            currentPoint = parent;//將當前結點指向父節點
            while(true){//循環遍歷節點，查找適合的插入位置
                if(currentPoint.value>value){
                    if(currentPoint.leftChild!=null){
                        currentPoint=currentPoint.leftChild;
                    }else{
                        currentPoint.leftChild=new Node(value,null,null);
                        length++;
                        break;
                    }
                }else{
                    if(currentPoint.rightChild!=null){
                        currentPoint=currentPoint.rightChild;
                    }else{
                        currentPoint.rightChild=new Node(value,null,null);
                        length++;
                        break;
                    }
                }
            }
        }
    }

中序遍歷二叉樹節點

public String visit(Node node) {
        sb.append(node.value+"(");
        if (node.leftChild != null) visit(node.leftChild);//遞歸遍歷左子樹
        if (node.rightChild != null) visit(node.rightChild);//遞歸遍歷右子樹
        sb.append(")");
        return sb.toString();
    }

總體代碼

public class BinaryTree {
    private Node parent;
    private Node currentPoint;
    private StringBuffer sb;
    private int length=0;

    class Node {
        private int value;
        private Node leftChild;
        private Node rightChild;

        public Node(int value, Node leftChild, Node rightChild) {
            this.value = value;
            this.leftChild = leftChild;
            this.rightChild = rightChild;
        }
    }
    public Node getParent(){
        return parent;
    }

    public BinaryTree() {
        sb=new StringBuffer();
    }

    public void insert(int value) {
        if (parent == null) {
            Node node = new Node(value, null, null);
            parent = node;
            length++;
        } else {
            currentPoint = parent;
            while(true){
                if(currentPoint.value>value){
                    if(currentPoint.leftChild!=null){
                        currentPoint=currentPoint.leftChild;
                    }else{
                        currentPoint.leftChild=new Node(value,null,null);
                        length++;
                        break;
                    }
                }else{
                    if(currentPoint.rightChild!=null){
                        currentPoint=currentPoint.rightChild;
                    }else{
                        currentPoint.rightChild=new Node(value,null,null);
                        length++;
                        break;
                    }
                }
            }
        }
    }

    public String visit(Node node) {
        sb.append(node.value+"(");
        if (node.leftChild != null) visit(node.leftChild);
        if (node.rightChild != null) visit(node.rightChild);
        sb.append(")");
        return sb.toString();
    }
    public int getLength(){
        return length;
    }

    @Override
    public String toString() {
        return visit(parent);
    }
}

main函數測試

public static void main(String[] args) {
        BinaryTree bt = new BinaryTree();
        bt.insert(1);
        bt.insert(3);
        bt.insert(2);
        bt.insert(5);
        bt.insert(6);
        bt.insert(7);
        bt.insert(8);
        bt.insert(9);
        bt.insert(10);
        bt.insert(11);
        bt.insert(12);
        bt.insert(13);
        bt.insert(14);
        bt.insert(15);
        System.out.println(bt.getLength());
        System.out.println(bt.toString());
    }