二叉树的镜像（java版）

//递归
public class Solution {
public void Mirror(TreeNode root) {
if(root == null){
return;
}
if(root != null){

if(root.left != null && root.right != null){
TreeNode tr = root.left;
root.left = root.right;
root.right = tr;
}else if(root.left != null && root.right == null){
TreeNode tr = root.left;
root.left = null;
root.right = tr;
}else if(root.left == null && root.right != null){
TreeNode tr = root.right;
root.right = null;
root.left = tr;
}else{
}
}
if(root.left != null){
Mirror(root.left);
}
if(root.right != null){
Mirror(root.right);
}
}
}

//非递归
import java.util.Stack;

public class Solution {
public void Mirror(TreeNode root) {
if(root == null){
return;
}
Stack<TreeNode> stack = new Stack<TreeNode>();
stack.push(root);
while(!stack.isEmpty()){
TreeNode node = stack.pop();
if(node.left != null||node.right != null){
TreeNode temp = node.left;
node.left = node.right;
node.right = temp;
}
if(node.left!=null){
stack.push(node.left);
}
if(node.right!=null){
stack.push(node.right);
}
}
}
}