二叉树的先序、中序、后序遍历

输入{1,2,3}
输出
[[1,2,3],[2,1,3],[2,3,1]]

java

public class Solution {
    /**
     * 
     * @param root TreeNode类 the root of binary tree
     * @return int整型二维数组
     */
    List<Integer> front = new ArrayList<>();
    List<Integer> mid = new ArrayList<>();
    List<Integer> back = new ArrayList<>();
    public int[][] threeOrders (TreeNode root) {
        // write code here
        PreorderTraversal(root);
        InorderTraversal(root);
        PostorderTraversal(root);
         
        int[][] res = {
            front.stream().mapToInt(Integer::valueOf).toArray(),
            mid.stream().mapToInt(Integer::valueOf).toArray(),
            back.stream().mapToInt(Integer::valueOf).toArray()
        };
         
        return res;
    }
     
    //前序遍历
    public void PreorderTraversal(TreeNode root){
        if(root == null)
            return;
        front.add(root.val);
        PreorderTraversal(root.left);
        PreorderTraversal(root.right);
    }
     
    //中序遍历
    public void InorderTraversal(TreeNode root){
        if(root == null)
            return;
        InorderTraversal(root.left);
        mid.add(root.val);
        InorderTraversal(root.right);
    }
     
    //后序遍历
    public void PostorderTraversal(TreeNode root){
        if(root == null)
            return;
        PostorderTraversal(root.left);
        PostorderTraversal(root.right);
        back.add(root.val);
    }
}
 

标签：TreeNode,InorderTraversal,PreorderTraversal,中序,二叉树,return,root,public,先序
来源： https://blog.csdn.net/qq_37185361/article/details/113831946