update

Author: dingjikerbo

leetcode/solution/src/ConstructStringFromBinaryTree.java

@@ -1,6 +1,14 @@
 /**
  * https://leetcode.com/articles/construct-string-from-binary-tree/
  */
+
+/**
+ * 这题不难，主要是搞清楚题目意思
+ * 即返回root + (左子树) + (右子树)
+ * 不过要注意几个特殊情况，如果左右子树都为null，则只返回root
+ * 如果左子树为null，右子树非null，则返回root + () + (右子树)
+ * 如果左子树非null，右子树为null，则返回root + (左子树)
+ */
 public class ConstructStringFromBinaryTree {
 
     /**

leetcode/src/Main.java

@@ -6,29 +6,12 @@ public class Main {
 
     public static class Solution {
 
-        public int kthSmallest(TreeNode root, int k) {
-            Stack<TreeNode> stack = new Stack<>();
-            while (!stack.isEmpty() || root != null) {
-                if (root != null) {
-                    stack.push(root);
-                    root = root.left;
-                } else {
-                    root = stack.pop();
 
-                    if (--k == 0) {
-                        return root.val;
-                    }
 
-                    root = root.right;
-                }
-            }
-            return -1;
-        }
     }
 
     public static void main(String[] args) {
         Solution s = new Solution();
-        TreeNode root1 = new TreeNode(1);
-        System.out.println(f);
+        System.out.println(a);
     }
 }