Create Range Sum of BST.java

varunu28 · web-flow · commit c290f14c2267 · 2021-12-13T17:48:31.000-08:00
diff --git a/Easy/Range Sum of BST.java b/Easy/Range Sum of BST.java
@@ -0,0 +1,37 @@
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+  public int rangeSumBST(TreeNode root, int low, int high) {
+    int[] rangeSum = {0};
+    helper(root, low, high, rangeSum);
+    return rangeSum[0];
+  }
+  
+  private void helper(TreeNode root, int low, int high, int[] rangeSum) {
+    if (root == null) {
+      return;
+    }
+    if (root.val >= low && root.val <= high) {
+      rangeSum[0] += root.val;
+    }
+    if (root.val >= low) {
+      helper(root.left, low, high, rangeSum);
+    }
+    if (root.val <= high) {
+      helper(root.right, low, high, rangeSum);
+    }
+  }
+}
