# range-sum-of-bst


Try it on <a href='https://leetcode.com/problems/range-sum-of-bst'>leetcode</a>

## Description
<div class="description">
<div><p>Given the <code>root</code> node of a binary search tree and two integers <code>low</code> and <code>high</code>, return <em>the sum of values of all nodes with a value in the <strong>inclusive</strong> range </em><code>[low, high]</code>.</p>

<p>&nbsp;</p>
<p><strong>Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/11/05/bst1.jpg" style="width: 400px; height: 222px;">
<pre><strong>Input:</strong> root = [10,5,15,3,7,null,18], low = 7, high = 15
<strong>Output:</strong> 32
<strong>Explanation:</strong> Nodes 7, 10, and 15 are in the range [7, 15]. 7 + 10 + 15 = 32.
</pre>

<p><strong>Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/11/05/bst2.jpg" style="width: 400px; height: 335px;">
<pre><strong>Input:</strong> root = [10,5,15,3,7,13,18,1,null,6], low = 6, high = 10
<strong>Output:</strong> 23
<strong>Explanation:</strong> Nodes 6, 7, and 10 are in the range [6, 10]. 6 + 7 + 10 = 23.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The number of nodes in the tree is in the range <code>[1, 2 * 10<sup>4</sup>]</code>.</li>
	<li><code>1 &lt;= Node.val &lt;= 10<sup>5</sup></code></li>
	<li><code>1 &lt;= low &lt;= high &lt;= 10<sup>5</sup></code></li>
	<li>All <code>Node.val</code> are <strong>unique</strong>.</li>
</ul>
</div>
</div>

## Solution(Python)
```Python
class Solution(object):
    def rangeSumBST(self, root, L, R):
        def dfs(node):
            if node:
                if L <= node.val <= R:
                    self.ans += node.val
                if L < node.val:
                    dfs(node.left)
                if node.val < R:
                    dfs(node.right)

        self.ans = 0
        dfs(root)
        return self.ans

```