二叉搜索树的范围和

938. 二叉搜索树的范围和

难度简单195

给定二叉搜索树的根结点 root，返回值位于范围 [low, high] 之间的所有结点的值的和。

示例 1：

输入：root = [10,5,15,3,7,null,18], low = 7, high = 15
输出：32

示例 2：

输入：root = [10,5,15,3,7,13,18,1,null,6], low = 6, high = 10
输出：23

提示：

• 树中节点数目在范围 [1, 2 * 104] 内
• 1 <= Node.val <= 105
• 1 <= low <= high <= 105
• 所有 Node.val 互不相同

中序遍历

/**
 * 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 {
    int low = 0;
    int high = 0;
    int sum = 0;
    public int rangeSumBST(TreeNode root, int low, int high) {
        this.low  = low;
        this.high = high;
        dfs(root);
        return sum;
    }

    public void dfs(TreeNode root){
        if(root==null)return;
        dfs(root.left);
        if(root.val>=low&&root.val<=high){
            sum += root.val;
        }
        dfs(root.right);
    }
}

赏

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