05 August 2008
Iterative
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/*
// Definition for a Node.
class Node {
public int val;
public List<Node> children;
public Node() {}
public Node(int _val) {
val = _val;
}
public Node(int _val, List<Node> _children) {
val = _val;
children = _children;
}
};
*/
class Solution {
public List<Integer> preorder(Node root) {
List<Integer> list = new ArrayList<>();
if (root == null) return list;
Stack<Node> stack = new Stack<>();
stack.add(root);
while (!stack.empty()) {
root = stack.pop();
list.add(root.val);
for (int i = root.children.size() - 1; i >= 0; i--)
stack.add(root.children.get(i));
}
return list;
}
}
Recursion
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class Solution {
public List<Integer> list = new ArrayList<>();
public List<Integer> preorder(Node root) {
if (root == null)
return list;
list.add(root.val);
for(Node node: root.children)
preorder(node);
return list;
}
}