#2466

Count Ways To Build Good Strings

specialist · 735 · lc medium +31 · verified · 59% accepted · 2,221 likes · top 56%

Description

Given integers zero, one, and low and high, count the number of strings of length between low and high (inclusive) that can be built by starting with an empty string and repeatedly appending either zero zeros or one ones.

Return the count modulo 10⁹ + 7.

Example 1:

Input: low = 3, high = 3, zero = 1, one = 1

Output: 8

Explanation:

One possible valid good string is "011".

It can be constructed as follows: "" -> "0" -> "01" -> "011".

All binary strings from "000" to "111" are good strings in this example.

Example 2:

Input: low = 2, high = 3, zero = 1, one = 2

Output: 5

Explanation: The good strings are "00", "11", "000", "110", and "011".

Code

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class Solution:
    def countGoodStrings(self, low: int, high: int, zero: int, one: int) -> int:

class Solution:
    def countGoodStrings(self, low: int, high: int, zero: int, one: int) -> int: