public class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode(){}
TreeNode(int val){
this.val = val;
}
public TreeNode(int val, TreeNode left, TreeNode right) {
this.val = val;
this.left = left;
this.right = right;
}
}
/*
递归的进行翻转
保存原来的右子树
*/
public class Solution1 {
public TreeNode invertTree(TreeNode root){
if(root == null){
return null;
}
//保存右子树
TreeNode rightTree = root.right;
root.left = invertTree(root.right);
root.right = invertTree(root.left);
return root;
}
}
import java.util.LinkedList;
import java.util.Queue;
//层序遍历,使用队列
public class Solution2 {
public TreeNode invertTree(TreeNode root){
if(root == null){
return null;
}
Queue<TreeNode> stack = new LinkedList<>();
stack.offer(root);
while(!stack.isEmpty()){
TreeNode node = stack.poll();
//保存右子树结点
TreeNode rightTree = node.right;
node.right = node.left;
node.left = rightTree;
if(node.left != null){
stack.offer(node.left);
}
if(node.right != null){
stack.offer(node.right);
}
}
return root;
}
}
public class Solution3 {
public TreeNode invertTree(TreeNode root){
if(root == null){
return null;
}
TreeNode left = invertTree(root.left);
TreeNode right = invertTree(root.right);
root.right = left;
root.left = right;
return root;
}
}