update

Author: yennanliu

leetcode_java/src/main/java/dev/workspace5.java

@@ -3472,52 +3472,85 @@ private String getMultiplyStr(String cur, Integer multiply) {
     // LC 776
     // https://leetcode.ca/2018-01-14-776-Split-BST/
     // https://leetcode.ca/all/776.html
-    // 10.09 am - 10.20 am
+    // 8.37 PM - 8.50 PM
     /**
      *   Idea : split tree
      *
      *   -> split tree into smaller, bigger array
      *   -> then build BST again from 2 arrays above
      */
+
+    // IDEA : DFS
+    TreeNode leftTree = new TreeNode();
+    TreeNode rightTree = new TreeNode();
     public TreeNode[] splitBST(TreeNode root, int target) {
+        TreeNode[] res = new TreeNode[2];
 
-        // split to 2 arrays
-        List<Integer> smaller = new ArrayList<>();
-        List<Integer> bigger = new ArrayList<>();
+        buildTreeDfs(root, target);
 
-        Queue<TreeNode> queue = new LinkedList<>();
-        queue.add(root);
+        res[0] = leftTree;
+        res[1] = rightTree; // ??
+        return res;
+    }
 
-        // bfs
-        while(!queue.isEmpty()){
-            // update array
-            TreeNode cur = queue.poll();
-            if (cur.val <= target){
-                smaller.add(cur.val);
-            }else{
-                bigger.add(cur.val);
-            }
-            // add to queue
-            if (cur.left != null){
-                queue.add(cur.left);
-            }
-            if (cur.right != null){
-                queue.add(cur.right);
-            }
+    private TreeNode[] buildTreeDfs(TreeNode root, int target){
+        if (root == null){
+            return null;
         }
+//        if (root.val <= target){
+//            // ??
+//            this.buildTreeDfs(leftTree, target);
+//        }else{
+//            // ?? or return
+//            this.buildTreeDfs(rightTree, target);
+//        }
+        if (root.left != null && root.left.val <= target){
 
-        // build tree
-        TreeNode smallerTree = buildTree(smaller);
-        TreeNode biggerTree = buildTree(bigger);
-
-        // collect result
-        TreeNode[] res = new TreeNode[2];
-        res[0] = smallerTree;
-        res[1] = biggerTree;
-
-        return res;
+            leftTree.left = root.left;
+            buildTreeDfs(leftTree, target);
+        }
+       return null;
     }
 
+//    public TreeNode[] splitBST(TreeNode root, int target) {
+//
+//        // split to 2 arrays
+//        List<Integer> smaller = new ArrayList<>();
+//        List<Integer> bigger = new ArrayList<>();
+//
+//        Queue<TreeNode> queue = new LinkedList<>();
+//        queue.add(root);
+//
+//        // bfs
+//        while(!queue.isEmpty()){
+//            // update array
+//            TreeNode cur = queue.poll();
+//            if (cur.val <= target){
+//                smaller.add(cur.val);
+//            }else{
+//                bigger.add(cur.val);
+//            }
+//            // add to queue
+//            if (cur.left != null){
+//                queue.add(cur.left);
+//            }
+//            if (cur.right != null){
+//                queue.add(cur.right);
+//            }
+//        }
+//
+//        // build tree
+//        TreeNode smallerTree = buildTree(smaller);
+//        TreeNode biggerTree = buildTree(bigger);
+//
+//        // collect result
+//        TreeNode[] res = new TreeNode[2];
+//        res[0] = smallerTree;
+//        res[1] = biggerTree;
+//
+//        return res;
+//    }
+
     private TreeNode buildTree(List<Integer> input){
         return null;
     }