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import { TreeNode } from "../mod.ts";
function buildTree(preorder: number[], inorder: number[]): TreeNode | null {    const map = new Map<number, number>();    for (let i = 0; i < inorder.length; i++) {        map.set(inorder[i], i);    }    function helper(        pStart: number,        pEnd: number,        iStart: number,        iEnd: number,    ): TreeNode | null {        if (pStart > pEnd) {            return null;        }        const rootVal = preorder[pStart];        const root = new TreeNode(rootVal);        const mid = map.get(rootVal) ?? 0;        const leftnum = mid - iStart;        root.left = helper(pStart + 1, pStart + leftnum, iStart, mid - 1);        root.right = helper(pStart + leftnum + 1, pEnd, mid + 1, iEnd);        return root;    }    return helper(0, preorder.length - 1, 0, inorder.length - 1);}export default buildTree;