0880. Decoded String at Index

https://leetcode.com/problems/decoded-string-at-index

Description

You are given an encoded string s. To decode the string to a tape, the encoded string is read one character at a time and the following steps are taken:

• If the character read is a letter, that letter is written onto the tape.

• If the character read is a digit d, the entire current tape is repeatedly written d - 1 more times in total.

Given an integer k, return the kth letter (1-indexed) in the decoded string.

Example 1:

**Input:** s = "leet2code3", k = 10
**Output:** "o"
**Explanation:** The decoded string is "leetleetcodeleetleetcodeleetleetcode".
The 10th letter in the string is "o".

Example 2:

**Input:** s = "ha22", k = 5
**Output:** "h"
**Explanation:** The decoded string is "hahahaha".
The 5th letter is "h".

Example 3:

**Input:** s = "a2345678999999999999999", k = 1
**Output:** "a"
**Explanation:** The decoded string is "a" repeated 8301530446056247680 times.
The 1st letter is "a".

Constraints:

• 2 <= s.length <= 100

• s consists of lowercase English letters and digits 2 through 9.

• s starts with a letter.

• 1 <= k <= 109

• It is guaranteed that k is less than or equal to the length of the decoded string.

• The decoded string is guaranteed to have less than 263 letters.

ac