94. Binary Tree Inorder Traversal

/**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public List<Integer> inorderTraversal(TreeNode root) {
//中序非递归方法

List<Integer> res=new ArrayList<Integer>();
Stack<TreeNode> st=new Stack<TreeNode>();
TreeNode temp=root;
while(temp!=null||!st.isEmpty())
{
// 将所有的节点都入栈，并且按照中序遍历的逆序进行入栈
if(temp==null)
{
temp=st.pop();
res.add(temp.val);
temp=temp.right;
}

else
{
st.push(temp);
temp=temp.left;
}

}
return res;
}
}