Jefferson-Aggor

const countSmallerToRight = (nums) => {
  // Helper: Binary Indexed Tree O(nlog(n))
  function BIT(size) {
    const tree = new Array(size + 1).fill(0);
    return {
      // Update the tree: add 'delta' at the given index
      update(index, delta) {
        index += 1;
        while (index < tree.length) {
          tree[index] += delta;