题解 | #寻找峰值#

/*
 * public class TreeNode {
 *   int val = 0;
 *   TreeNode left = null;
 *   TreeNode right = null;
 *   public TreeNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param root TreeNode类 
     * @return int整型一维数组
     */
    public int[] postorderTraversal (TreeNode root) {
        // write code here
        if (root == null){
                return new int[0];
            }
            List<Integer> resultList = new ArrayList<>();
            tailorder(root,resultList);
            return resultList.stream().mapToInt(Integer::intValue).toArray();
    }
    public void tailorder(TreeNode root,List<Integer> resultList){
            if (root.left !=null){
                tailorder(root.left,resultList);
            }
            if (root.right != null){
                tailorder(root.right,resultList);
            }
            resultList.add(root.val);
        }
}