二叉树递归遍历（前序，中序，后序）

1.Java 中没有 Tree 的数据结构，不过我们可以自己写一个：

  

public class TreeNode {

    int val;
    TreeNode left;
    TreeNode right;

    public TreeNode(int val) {
        this.val = val;
    }

    public TreeNode(int val, TreeNode left, TreeNode right) {
        this.val = val;
        this.left = left;
        this.right = right;
    }
}

2.初始化遍历的树

                                                     

.

        TreeNode t4=new TreeNode(4,null,null);
        TreeNode t8=new TreeNode(8,null,null);
        TreeNode t6=new TreeNode(6,t4,t8);
        TreeNode t12=new TreeNode(12,null,null);
        TreeNode t16=new TreeNode(16,null,null);
        TreeNode t14=new TreeNode(14,t12,t16);
        TreeNode t10=new TreeNode(10,t6,t14);

 

3.前序遍历

    public  static  void preOrder(TreeNode treeNode){
        System.out.println(treeNode.val);
        if(treeNode.left!=null){
            preOrder(treeNode.left);
        }
        if(treeNode.right!=null){
            preOrder(treeNode.right);
        }
    }

 

4.中序遍历（值从小到大遍历）

 public  static void  inOrder(TreeNode treeNode){
        if(treeNode.left!=null){
            inOrder(treeNode.left);
        }
        System.out.println(treeNode.val);
        if(treeNode.right!=null){
            inOrder(treeNode.right);
        }
    }

 

5.后序遍历

 public static  void postOrder(TreeNode treeNode){
        if(treeNode.left!=null){
            postOrder(treeNode.left);
        }
        if(treeNode.right!=null){
            postOrder(treeNode.right);
        }
        System.out.println(treeNode.val);
    }

 

来源：CSDN

作者：风起尘落

链接：https://blog.csdn.net/qq_34707456/article/details/103927827