二叉树遍历非递归

先序遍历：

public void preorderIterative() {

Stack<Node> stack = new Stack<Node>();

Node p = root;

if (p != null) {

stack.push(p);

while (!stack.empty()) {

p = stack.pop();

visit(p);

if (p.right != null)

stack.push(p.right);

if (p.left != null)

stack.push(p.left);

}

}

}

中序遍历：

public void inorderIterative() {

Stack<Node> stack = new Stack<Node>();

Node p = root;

while (p != null) {

while (p != null) {

if (p.right != null)

stack.push(p.right);

stack.push(p);

p = p.left;

}

p = stack.pop();

while (!stack.empty() && p.right == null) {

visit(p);

p = stack.pop();

}

visit(p);

if (!stack.empty())

p = stack.pop();

else

p = null;

}

}

后序遍历：

public void postorderIterative() {

Stack<Node> stack = new Stack<Node>();

Node p = root;

Node q = root;

while (p != null) {

while (p.left != null) {

stack.push(p);

p = p.left;

}

while (p != null && (p.right == null || p.right == q)) {

visit(p);

q = p;

if (stack.empty())

return;

p = stack.pop();

}

stack.push(p);

p = p.right;

}

}