代码
没什么可以说的，代码很简单。
// 递归前序遍历
public void preOrder1(TreeNode root){
if (root != null) {
System.out.println(root.val);
preOrder1(root.left);
preOrder1(root.right);
}
}
// 前序遍历非递归
public void preOrder(TreeNode root){
Stack<TreeNode> stack = new Stack<>();
while (root != null || !stack.isEmpty()) {
while (root != null) {
System.err.println(root.val);
stack.push(root);
root = root.left;
}
while (!stack.isEmpty()) {
root = stack.pop();
root = root.right;
}
}
}
// 中序遍历递归
public void inOrder1(TreeNode root){
if (root!= null) {
inOrder1(root.left);
System.out.println(root.val);
inOrder1(root.right);
}
}
// 中序遍历非递归
public void inOder2(TreeNode root){
Stack<TreeNode> stack = new Stack<>();
while (!stack.isEmpty() || root != null) {
while (root != null) {
stack.push(root);
root = root.left;
}
if (!stack.isEmpty()) {
root = stack.pop();
System.out.println(root.val);
root = root.right;
}
}
}
// 后序遍历递归
public void lateOrder1(TreeNode root) {
if (root != null) {
lateOrder1(root.left);
lateOrder1(root.right);
System.out.println(root.val);
}
}
// 后序遍历的非递归
public void lateOrder2(TreeNode root){
Stack<TreeNode> stack1 = new Stack<>();
Stack< TreeNode> tempStack = new Stack<>();
while (root != null || stack1.isEmpty() == false) {
while(root != null){
stack1.push(root);
tempStack.push(root);
root = root.right;
}
if (!stack1.isEmpty()) {
root = stack1.pop();
root = root.left;
}
}
while (tempStack.isEmpty() == true) {
root = tempStack.pop();
System.out.println(root.val);
}
}
