二叉树的遍历

public class BinaryTreeTest {
    //节点类，使用链表的方式实现树；
    @Data
    public static class Node {
        private char data;
        private Node left;
        private Node right;
        public Node(char data, Node left, Node right) {
            this.data = data;
            this.left = left;
            this.right = right;
        }
    }
    public static void main(String[] args) {
        //构建一颗二叉树 ABCDEFGHK
        Node D = new Node('D', null, null);
        Node H = new Node('H', null, null);
        Node K = new Node('K', null, null);
        Node C = new Node('C', D, null);
        Node G = new Node('G', H, K);
        Node B = new Node('B', null, C);
        Node F = new Node('F', G, null);
        Node E = new Node('E', null, F);
        Node A = new Node('A', B, E);
        //根节点是a，二叉树的三种遍历方式
        //前序：根  左   右   ABCDEFGHK
        //中序：左  根   右   BDCAEHGKF
        //后序：左  右   根   DCBHKGFEA
        preErgodic(A);
        System.out.println();
        midErgodic(A);
        System.out.println();
        lastErgodic(A);
    }
    //前序
    public static void preErgodic(Node root){
        System.out.print(root.getData());
        if(root.getLeft() != null){
            preErgodic(root.getLeft());
        }
        if(root.getRight() != null){
            preErgodic(root.getRight());
        }
    }
    //中序
    public static void midErgodic(Node root){
        if(root.getLeft() != null){
            midErgodic(root.getLeft());
        }
        System.out.print(root.getData());
        if(root.getRight() != null){
            midErgodic(root.getRight());
        }
    }
    //后序
    public static void lastErgodic(Node root){
        if(root.getLeft() != null){
            lastErgodic(root.getLeft());
        }
        if(root.getRight() != null){
            lastErgodic(root.getRight());
        }
        System.out.print(root.getData());
    }
}