剑指Offer:面试题19——二叉树的镜像(java实现)

public class TreeNode {
int val = 0;
TreeNode left = null;
TreeNode right = null;

public TreeNode(int val) {
this.val = val;

}

}

8
/  \
6   10
/ \  / \
5  7 9 11
镜像二叉树
8
/  \
10   6
/ \  / \
11 9 7  5

public void Mirror(TreeNode root) {

if(root == null){
return;
}

if(root.left == null && root.right == null){
return;
}

TreeNode tmp = root.left;
root.left = root.right;
root.right = tmp;

if(root.left != null){//这里加入判空条件可以及时终止递归，会少进行一次递归，减少栈存储的压力
Mirror(root.left);
}
if(root.right != null){
Mirror(root.right);
}
}