1234567891011121314151617181920
import { le as binarySearch } from "https://esm.sh/@masx200/binary-search-bounds@2.0.5";
import { BinaryIndexTree } from "../rank-from-stream-lcci/index.ts";
export default function reversePairs(nums: number[]): number {    const n = nums.length;    const tmp = Array.from(nums);    tmp.sort((a, b) => a - b);    for (let i = 0; i < n; ++i) {        nums[i] = binarySearch(tmp, nums[i]) + 1;    }    const bit = new BinaryIndexTree(n);    let ans = 0;    for (let i = n - 1; i >= 0; i--) {        ans += bit.query(nums[i] - 1);        bit.update(nums[i], 1);    }    return ans;}