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import { TreeNode } from "../mod.ts";
export function buildBST(    start: number,    end: number,    get: () => number | undefined,    next: () => void,): TreeNode | null {    if (start > end) return null;
    const mid = Math.floor((start + end) / 2);    const root = new TreeNode();    const left = buildBST(start, mid - 1, get, next);
    root.left = left;    root.val = get() ?? 0;    next();    const right = buildBST(mid + 1, end, get, next);
    root.right = right;    //  console.log(JSON.stringify(root))    return root;}