lena_sort.py

import sys
sys.setrecursionlimit(100000)


def main(length, comp, offset, min_vals, max_vals, ans):
    if length == 0:
        return
    if length == 1:
        ans.append(offset)
        return
    pivot = 0
    comp -= (length - 1)
    while True:
        if min_vals[pivot] + min_vals[length - pivot - 1] <= comp <= max_vals[pivot] + max_vals[length - pivot - 1]:
            break
        pivot += 1

    left = min_vals[pivot]
    right = comp - left
    while True:
        if min_vals[length - pivot - 1] <= right <= max_vals[length - pivot - 1]:
            break
        left += 1
        right -= 1

    ans.append(pivot + offset)
    main(pivot, left, offset, min_vals, max_vals, ans)
    main(length - pivot - 1, comp - left, offset + pivot + 1, min_vals, max_vals, ans)


if __name__ == "__main__":
    q = int(input())
    for q_itr in range(q):
        inp = input().split()
        l = int(inp[0])
        c = int(inp[1])

        maxs = [0,0]
        mins = [0,0]
        for i in range(1, l):
            maxs.append(maxs[i] + i)
            mins.append(i + mins[i // 2] + mins[i - i // 2])
        if c < mins[-1] or c > maxs[-1]:
            print(-1)
        else:
            result = []
            main(l, c, 1, mins, maxs, result)
            print(*result)