樹的排序算法 前序 中序 後序

樹節點 保存結點值，左子樹，右子樹

public class TreeNode {
    private String value;
    private  TreeNode left;
    private  TreeNode right;

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }

    public TreeNode getLeft() {
        return left;
    }

    public void setLeft(TreeNode left) {
        this.left = left;
    }

    public TreeNode getRight() {
        return right;
    }

    public void setRight(TreeNode right) {
        this.right = right;
    }

    public TreeNode(String value, TreeNode left, TreeNode right) {
        this.value = value;
        this.left = left;
        this.right = right;
    }

    @Override
    public String toString() {
        return "TreeNode{" +
                "value='" + value + '\'' +
                ", left=" + left +
                ", right=" + right +
                '}';
    }
}

初始化一個樹形狀爲

前序 中序 後序排序算法

public class Tree {
    private TreeNode root;
    private List<TreeNode> result=new ArrayList<TreeNode>();

    public TreeNode getRoot() {
        return root;
    }

    public void setRoot(TreeNode root) {
        this.root = root;
    }

    public List<TreeNode> getResult() {
        return result;
    }

    public void setResult(List<TreeNode> result) {
        this.result = result;
    }
    public Tree(){
        init();
    }

    private void init() {
        TreeNode g=new TreeNode("G",null,null);
        TreeNode x=new TreeNode("X",null,null);
        TreeNode y=new TreeNode("Y",null,null);
        TreeNode d=new TreeNode("D",x,y);
        TreeNode b=new TreeNode("B",d,null);
        TreeNode e=new TreeNode("E",g,null);
        TreeNode f=new TreeNode("F",null,null);
        TreeNode c=new TreeNode("C",e,f);
        TreeNode a=new TreeNode("A",b,c);
        root=a;
    }

    /**
     * 計算深度
     * @param node
     * @return
     */
    public int calDepth(TreeNode node){
        if (node.getLeft()==null&&node.getRight()==null){
            return 1;
        }
        int leftDepth=0;
        int rightDepth=0;
        if(node.getLeft()!=null){
            leftDepth=calDepth(node.getLeft());
        }
        if(node.getRight()!=null){
            rightDepth=calDepth(node.getRight());
        }
        System.out.println("左"+leftDepth+"右"+rightDepth);
        int temp=leftDepth>rightDepth?leftDepth+1:rightDepth+1;
        System.out.println("中間計算結果"+temp);
        return temp;
    }
    //前序遍歷  根左右
    public void perOrder(TreeNode root){
        if(root==null){
            return;
        }
        result.add(root);
        if(root.getLeft()!=null){
            perOrder(root.getLeft());
        }
        if(root.getRight()!=null){
            perOrder(root.getRight());
        }
    }
    //中序遍歷   左根右
    public void InMiddleOrder(TreeNode root){
        if(root==null){
            return;
        }
        if(root.getLeft()!=null){
            InMiddleOrder(root.getLeft());
        }
        result.add(root);
        if(root.getRight()!=null){
            InMiddleOrder(root.getRight());
        }
    }
    //後序遍歷   左右根
    public void LastOrder(TreeNode root){
        if(root==null){
            return;
        }
        if(root.getLeft()!=null){
            LastOrder(root.getLeft());
        }
        if(root.getRight()!=null){
            LastOrder(root.getRight());
        }
        result.add(root);
    }





}

測試程序

public class SearchTree {
    public static void main(String[] args) {
        Tree tree=new Tree();
        System.out.println("根節點"+tree.getRoot().getValue());
        //先序遍歷
        tree.perOrder(tree.getRoot());
        System.out.println("樹的深度是"+tree.calDepth(tree.getRoot()));
        System.out.println("先序遍歷結果是：");
        for (TreeNode eNode  :tree.getResult() ) {
            System.out.print(eNode.getValue()+" ");
        }
        tree.getResult().clear();
        tree.InMiddleOrder(tree.getRoot());
        System.out.println("中序遍歷結果是：");
        for (TreeNode eNode  :tree.getResult() ) {
            System.out.print(eNode.getValue()+" ");
        }
        tree.getResult().clear();
        tree.LastOrder(tree.getRoot());
        System.out.println("後序遍歷結果是：");
        for (TreeNode eNode  :tree.getResult() ) {
            System.out.print(eNode.getValue()+" ");
        }

    }


}