镜像二叉树

手动压栈

import java.util.Stack;
public class Solution {
  public void Mirror(TreeNode root) {

    // 空树
    if (root == null) {
      return;
    }
    // 左右均为空
    if (root.left == null && root.right == null) {
      return;
    }

    // 用来遍历的栈
    Stack<TreeNode> stack = new Stack<TreeNode>();

    stack.push(root);

    TreeNode curNode;
    TreeNode tempNode;

    // 深度优先
    while (!stack.isEmpty()) {
      curNode = stack.pop();
      if(curNode == null) {
        continue;
      }
      if(curNode.left == null && curNode.right==null) {
        continue;
      }
      // 交换
      tempNode = curNode.left;
      curNode.left = curNode.right;
      curNode.right = tempNode;
      stack.push(curNode.left);
      stack.push(curNode.right);
    }
  }
}