剑指offer_19

题意：二叉树镜像
思路：看代码，鲁棒性要处理好，对于空节点的处理。
代码：

package MianShiTi_19;

public class MianShiTi_19 {
    public static class BinaryNode{
        int value;
        BinaryNode left;
        BinaryNode right;
    }
    public static void mirrorTree(BinaryNode node) throws Exception {
        if(node == null){
            return;
        }
        if(node.left == null && node.right == null){
            return;
        }
        if(node != null){
        BinaryNode tempNode = null;
        tempNode = node.left;
        node.left = node.right;
        node.right = tempNode;
        //对子树进行处理
        mirrorTree(node.left);
        mirrorTree(node.right);
        }
    }

    public static void printTree(BinaryNode node) {
        if(node != null){
        System.out.print(node.value+" ");
        printTree(node.left);
        printTree(node.right);
        }
    }

    public static void main(String[] args) throws Exception {
        BinaryNode root = new BinaryNode();
        root.value = 8 ;
        root.left = new BinaryNode();
        root.left.value = 6;
        root.right = new BinaryNode();
        root.right.value = 10;
        root.left.left = new BinaryNode();
        root.left.left.value = 5;
        root.left.right = new BinaryNode();
        root.left.right.value = 7;
        root.right.left = new BinaryNode();
        root.right.left.value = 9;
        root.right.right = new BinaryNode();
        root.right.right.value = 11;

        printTree(root);
        mirrorTree(root);
        System.out.println();
        printTree(root);
        }
    }