Bob is standing at cell (0, 0) , and he wants to reach destination : (row, column) . He can only travel right and down . You are going to help Bob by providing instructions for him to reach destination .
The instructions are represented as a string, where each character is either:
'H' , meaning move horizontally (go right ), or
'V' , meaning move vertically (go down ).
Multiple instructions will lead Bob to destination . For example, if destination is (2, 3) , both "HHHVV" and "HVHVH" are valid instructions .
However, Bob is very picky. Bob has a lucky number k , and he wants the k ^th lexicographically smallest instructions that will lead him to destination . k is 1-indexed .
Given an integer array destination and an integer k , return the k ^th lexicographically smallest instructions that will take Bob to destination .
destination.length == 21 <= row, column <= 151 <= k <= nCr(row + column, row) , where nCr(a, b) denotes a choose b .