09-27 leetcode 0880

题目

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.

题解

这题没啥好说的。。直接暴力写就行（

class Solution:
    def decodeAtIndex(self, s: str, k: int) -> str:
        length = 0
        for char in s:
            if char.isdigit():
                length *= int(char)
            else:
                length += 1
        for char in reversed(s):
            k %= length
            if k == 0 and char.isalpha():
                return char
            if char.isdigit():
                length //= int(char)
            else:
                length -= 1
        return ""

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