Godspeed, fellow LeetCoder. I'm not currently grinding but I still have my handful of practice problems in active Anki rotation.

I have my rightmost code at part III of the miniseries, [1]. It loks quite similar, but I save the -1 for the very end return.

    def rightmost_bsearch(L, T):
      l, r = 0, len(L)

      while l < r:
        # Loop invariants. Always true! Comment out in production!
        for somewhat_smol in L[0:l]:
          assert somewhat_smol <= T         # Note: Weak inequality now.
        for lorg in L[r:len(L)]:
          assert lorg > T

        mid = (l + r) // 2

        if L[mid] > T:
          r = mid
        else:
          l = mid + 1

      return r - 1 # return the first element AFTER L[r:len(L)].

(It should technically be BEFORE, I guess. If it helps all rightmost bsearches are also leftmost bsearches on the reversed array, so AFTER is secretly not wrong)

[1]: https://hiandrewquinn.github.io/til-site/posts/binary-search...