题目

二叉树及三种顺序的递归遍历

思路

代码

/*** @Author: ggdpzhk* @CreateTime: 2024-08-04** 二叉树及三种顺序的递归遍历* LeetCode 144. 二叉树的前序遍历* LeetCode 94. 二叉树的中序遍历* LeetCode 145. 二叉树的后序遍历* LeetCode 102. 二叉树的层序遍历*/
public class _017_Tree {public static void main(String[] args) {TreeNode head = new TreeNode(1);head.left = new TreeNode(2);head.right = new TreeNode(3);head.left.left = new TreeNode(4);head.left.right = new TreeNode(5);head.right.left = new TreeNode(6);head.right.right = new TreeNode(7);System.out.println("先序遍历递归版");preOrder(head);System.out.println();System.out.println("中序遍历递归版");inOrder(head);System.out.println();System.out.println("后序遍历递归版");postOrder(head);System.out.println();}public static class TreeNode {int val;TreeNode left;TreeNode right;TreeNode(int x) {val = x;}}//先序打印所有节点 递归版public static void preOrder(TreeNode head) {if (head == null) {return;}System.out.print(head.val + " ");//先遍历我自己preOrder(head.left);//再遍历左子树preOrder(head.right);//再遍历右子树}//中序打印所有节点，递归版public static void inOrder(TreeNode head) {if (head == null) {return;}inOrder(head.left);System.out.print(head.val+" ");//左树结束，回到我，打印我inOrder(head.right);}//后序打印所有节点，递归版public static void postOrder(TreeNode head) {if(head == null){return;}postOrder(head.left);postOrder(head.right);System.out.print(head.val+" ");//左树右树遍历结束，回到我，打印我}
}

运行结果