Question

Solution

题目大意：后序遍历一个树

思路：

1）递归

2）迭代

Java实现（递归）：

public List
    
      postorder(Node root) {    List
     
       ansList = new ArrayList<>();    recursivePostorder(root, ansList);    return ansList;}void recursivePostorder(Node root, List
      
        ansList) {    if (root == null) return;    if (root.children != null) {        for (Node tmp : root.children) {            recursivePostorder(tmp, ansList);        }    }    ansList.add(root.val);}
      
     
    

Java实现（迭代）：

public List
    
      postorder(Node root) {    List
     
       ansList = new ArrayList<>();    if (root == null) return ansList;    List
      
        nodeList = new ArrayList<>();    nodeList.add(root);    while (nodeList.size() > 0) {        Node cur = nodeList.get(nodeList.size() - 1);        nodeList.remove(nodeList.size() - 1);        ansList.add(cur.val);        if (cur.children != null) {            for (Node tmp : cur.children) {                nodeList.add(tmp);            }        }    }    for (int i=0; i