二叉树的遍历

二叉树结点的定义与先序（中左右）、中序（左中右）、后序（左右中）遍历，顺便写个最大深度，都是递归实现，之后再学习非递归的方法。



先序遍历的结果为：5,2,4,1,3,8,4,2,9，中序遍历的结果：4,2,1,5,4,8,2,3,9，后序遍历结果：4,1,2,4,2,8,9,3,5。

package leetcode;

class TreeNode
{
TreeNode left;
TreeNode right;
int val;
TreeNode(int val)
{
this.val = val;
}
static int getDepth(TreeNode root)
{
if(root==null)
{
return 0;
}
int right = getDepth(root.right);
int left = getDepth(root.left);
return left>right?left+1:right+1;
}
static void scanNodes(TreeNode root)
{
if(root==null)
{
return;
}
//System.out.println(root.val); //先序遍历
scanNodes(root.left);
//System.out.println(root.val); //中序遍历
scanNodes(root.right);
System.out.println(root.val); //后序遍历
}
public static void main(String[] args)
{
TreeNode root = new TreeNode(5);
TreeNode left1 = new TreeNode(2);
TreeNode left2 = new TreeNode(1);
TreeNode left3 = new TreeNode(4);
TreeNode right1 = new TreeNode(3);
TreeNode right2 = new TreeNode(8);
TreeNode right3 = new TreeNode(9);
TreeNode right4 = new TreeNode(4);
TreeNode right5 = new TreeNode(2);
root.left = left1;
left1.right = left2;
left1.left = left3;
root.right = right1;
right1.left = right2;
right1.right = right3;
right2.left = right4;
right2.right = right5;
scanNodes(root);
System.out.println("The depth of BinaryTree is: "+getDepth(root));
}

}