愛比的新手筆記

Given the root node of a binary search tree and two integers low and high, return the sum of values of all nodes with a value in the inclusive range [low, high].

Example 1:

Input: root = [10,5,15,3,7,null,18], low = 7, high = 15 Output: 32 Explanation: Nodes 7, 10, and 15 are in the range [7, 15]. 7 + 10 + 15 = 32.

Example 2:

Input: root = [10,5,15,3,7,13,18,1,null,6], low = 6, high = 10 Output: 23 Explanation: Nodes 6, 7, and 10 are in the range [6, 10]. 6 + 7 + 10 = 23.

Constraints:

• The number of nodes in the tree is in the range [1, 2 * 104].
• 1 <= Node.val <= 105
• 1 <= low <= high <= 105
• All Node.val are unique.

這題非常簡單, 只是加一加, 所以大家的答案都差不多, 但速度落差很大, 應該是被LeetCode server當時的忙碌程度影響

private int sum = 0;
public int RangeSumBST(TreeNode root, int low, int high)
{
    if (root == null) return sum;
    if (root.val <= high && root.val >= low)
        sum += root.val;
    if (root.val > low) RangeSumBST(root.left, low, high);
    if (root.val < high) RangeSumBST(root.right, low, high);
    return sum;
}

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