leetcode-solutions/leetcode145.java at master · utkarsh684/leetcode-solutions · GitHub

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/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
import java.util.*;
class leetcode145 {
    public List<Integer> postorderTraversal(TreeNode root) {
        List<Integer> list=new ArrayList<>();

        postorder(root,list);
        return list;

    }

    void postorder(TreeNode root,List<Integer> list){
        if(root==null){
            return ;
        }

        postorder(root.left,list);
        postorder(root.right,list);
        list.add(root.val);
    }
}