g1601_1700.s1643_kth_smallest_instructions

Class Solution

java.lang.Object

g1601_1700.s1643_kth_smallest_instructions.Solution

public class Solution
extends Object

1643 - Kth Smallest Instructions.

Hard

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 kth lexicographically smallest instructions that will lead him to destination. k is 1-indexed.

Given an integer array destination and an integer k, return the kth lexicographically smallest instructions that will take Bob to destination.

Example 1:

Input: destination = [2,3], k = 1

Output: “HHHVV”

Explanation: All the instructions that reach (2, 3) in lexicographic order are as follows: [“HHHVV”, “HHVHV”, “HHVVH”, “HVHHV”, “HVHVH”, “HVVHH”, “VHHHV”, “VHHVH”, “VHVHH”, “VVHHH”].

Example 2:

Input: destination = [2,3], k = 2

Output: “HHVHV”

Example 3:

Input: destination = [2,3], k = 3

Output: “HHVVH”

Constraints:

• destination.length == 2
• 1 <= row, column <= 15
• 1 <= k <= nCr(row + column, row), where nCr(a, b) denotes a choose b.

Constructor Summary

Constructors

Constructor and Description
Solution()

Method Summary

Modifier and Type	Method and Description
String	kthSmallestPath(int[] destination, int k)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Solution

public Solution()

Method Detail

kthSmallestPath

public String kthSmallestPath(int[] destination,
                              int k)