g1501_1600.s1545_find_kth_bit_in_nth_binary_string

Class Solution

java.lang.Object

g1501_1600.s1545_find_kth_bit_in_nth_binary_string.Solution

public class Solution
extends Object

1545 - Find Kth Bit in Nth Binary String.

Medium

Given two positive integers n and k, the binary string Sn is formed as follows:

• S1 = "0"
• Si = Si - 1 + “1” + reverse(invert(Si - 1)) for i > 1

Where + denotes the concatenation operation, reverse(x) returns the reversed string x, and invert(x) inverts all the bits in x (0 changes to 1 and 1 changes to 0).

For example, the first four strings in the above sequence are:

• S1 = "0"
• S2 = "0**1**1"
• S3 = "011**1**001"
• S4 = "0111001**1**0110001"

Return the kth bit in Sn. It is guaranteed that k is valid for the given n.

Example 1:

Input: n = 3, k = 1

Output: “0”

Explanation: S₃ is “0111001”. The 1^st bit is “0”.

Example 2:

Input: n = 4, k = 11

Output: “1”

Explanation: S₄ is “0111001101**1**0001”. The 11^th bit is “1”.

Constraints:

• 1 <= n <= 20
• 1 <= k <= 2n - 1

Constructor Summary

Constructors

Constructor and Description
Solution()

Method Summary

Modifier and Type	Method and Description
char	findKthBit(int n, 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

findKthBit

public char findKthBit(int n,
                       int k)