0779. K-th Symbol in Grammar

https://leetcode.com/problems/k-th-symbol-in-grammar

Description

We build a table of n rows (1-indexed). We start by writing 0 in the 1st row. Now in every subsequent row, we look at the previous row and replace each occurrence of 0 with 01, and each occurrence of 1 with 10.

• For example, for n = 3, the 1st row is 0, the 2nd row is 01, and the 3rd row is 0110.

Given two integer n and k, return the kth (1-indexed) symbol in the nth row of a table of n rows.

Example 1:

**Input:** n = 1, k = 1
**Output:** 0
**Explanation:** row 1: 0

Example 2:

**Input:** n = 2, k = 1
**Output:** 0
**Explanation:**
row 1: 0
row 2: 01

Example 3:

**Input:** n = 2, k = 2
**Output:** 1
**Explanation:**
row 1: 0
row 2: 01

Example 4:

**Input:** n = 3, k = 1
**Output:** 0
**Explanation:**
row 1: 0
row 2: 01
row 3: 0110

Constraints:

• 1 <= n <= 30

• 1 <= k <= 2n - 1

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