前序遍历非递归
然后node再进行前序遍历
中序遍历非递归
让node.right进行中序遍历
后续遍历非递归
public void preorder(Visitor<E> visitor) {
if (visitor == null || root == null) return;
Stack<Node<E>> stack = new Stack<>();
stack.push(root);
while (!stack.isEmpty()) {
Node<E> node = stack.pop();
// 访问node节点
if (visitor.visit(node.element)) return;
if (node.right != null) {
stack.push(node.right);
}
if (node.left != null) {
stack.push(node.left);
}
}
}
public void preorder2(Visitor<E> visitor) {
if (visitor == null || root == null) return;
Node<E> node = root;
Stack<Node<E>> stack = new Stack<>();
while (true) {
if (node != null) {
// 访问node节点
if (visitor.visit(node.element)) return;
// 将右子节点入栈
if (node.right != null) {
stack.push(node.right);
}
// 向左走
node = node.left;
} else if (stack.isEmpty()) {
return;
} else {
// 处理右边
node = stack.pop();
}
}
}
public void inorder(Visitor<E> visitor) {
if (visitor == null || root == null) return;
Node<E> node = root;
Stack<Node<E>> stack = new Stack<>();
while (true) {
if (node != null) {
stack.push(node);
// 向左走
node = node.left;
} else if (stack.isEmpty()) {
return;
} else {
node = stack.pop();
// 访问node节点
if (visitor.visit(node.element)) return;
// 让右节点进行中序遍历
node = node.right;
}
}
}
public void postorder(Visitor<E> visitor) {
if (visitor == null || root == null) return;
// 记录上一次弹出访问的节点
Node<E> prev = null;
Stack<Node<E>> stack = new Stack<>();
stack.push(root);
while (!stack.isEmpty()) {
Node<E> top = stack.peek();
if (top.isLeaf() || (prev != null && prev.parent == top)) {
prev = stack.pop();
// 访问节点
if (visitor.visit(prev.element)) return;
} else {
if (top.right != null) {
stack.push(top.right);
}
if (top.left != null) {
stack.push(top.left);
}
}
}
}