树，为了更加熟悉使用，这里将在LeetCode收集树的一些题。
LeetCode-94-mid(二叉树的中序遍历)
给定一个二叉树，返回它的中序 遍历。
示例:
输入: [1,null,2,3]
1
\
2
/
3
输出: [1,3,2]
public class LeetCode94 {
public static void main(String[] args) {
TreeNode94 head= new TreeNode94(1);
head.left=null;
head.right= new TreeNode94(2);
head.right.left=new TreeNode94(3);
List<Integer> list =(new Solution94()).inorderTraversal(head);
for (int i = 0; i < list.size(); i++) {
System.out.printf(list.get(i)+",");
}
}
}
class Solution94 {
public List<Integer> inorderTraversal(TreeNode94 root) {
List<Integer> list=new ArrayList<>();
Stack<TreeNode94> stack= new Stack<>();
TreeNode94 cur=root;
while (cur!=null|| !stack.isEmpty()){
if(cur!=null){
stack.push(cur);
cur=cur.left;
}else{
cur = stack.pop();
list.add(cur.val);
cur= cur.right;
}
}
return list;
}
}
class TreeNode94 {
int val;
TreeNode94 left;
TreeNode94 right;
TreeNode94(int x) { val = x; }
}