Java二叉树遍历

        我这边使用的是内部类创建节点

  static class Node {
        private String value;
        private Node left;
        private Node right;

        public Node(String value) {
            this.value = value;
        }
    }

给节点添加数据

  Node nodeA = new Node("A");
  Node nodeB = new Node("B");
  Node nodeC = new Node("C");
  Node nodeD = new Node("D");
  Node nodeE = new Node("E");
  Node nodeF = new Node("F");
  Node nodeG = new Node("G");
  nodeA.left = nodeB;
  nodeA.right = nodeC;
  nodeB.left = nodeD;
  nodeB.right = nodeE;
  nodeC.left = nodeF;
  nodeD.left = nodeG;

   前序遍历

public static void list1(Node node) {
        if (node == null) return;
        System.out.print(node.value);
        list1(node.left);
        list1(node.right);
    }

中序遍历

 public static void list2(Node node) {
        if (node == null) return;
        list2(node.left);
        System.out.print(node.value);
        list2(node.right);
    }

 后序遍历

 public static void list3(Node node) {
        if (node == null) return;
        list3(node.left);
        list3(node.right);
        System.out.print(node.value);
    }

层次遍历

 public static void no1(Node node){
        if(node==null){
            return;
        }
        Queue queue = new LinkedList<>();
        queue.add(node);
        while (!queue.isEmpty()){
            Node node1 = queue.poll();
            System.out.print(node1.value);
            if(node1.left!=null) queue.add(node1.left);
            if(node1.right!=null) queue.add(node1.right);
        }
    }

效果