{ "data": { "question": { "questionId": "2562", "questionFrontendId": "2466", "boundTopicId": null, "title": "Count Ways To Build Good Strings", "titleSlug": "count-ways-to-build-good-strings", "content": "

Given the integers zero, one, low, and high, we can construct a string by starting with an empty string, and then at each step perform either of the following:

\n\n\n\n

This can be performed any number of times.

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A good string is a string constructed by the above process having a length between low and high (inclusive).

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Return the number of different good strings that can be constructed satisfying these properties. Since the answer can be large, return it modulo 109 + 7.

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\n

Example 1:

\n\n
\nInput: low = 3, high = 3, zero = 1, one = 1\nOutput: 8\nExplanation: \nOne possible valid good string is "011". \nIt can be constructed as follows: "" -> "0" -> "01" -> "011". \nAll binary strings from "000" to "111" are good strings in this example.\n
\n\n

Example 2:

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\nInput: low = 2, high = 3, zero = 1, one = 2\nOutput: 5\nExplanation: The good strings are "00", "11", "000", "110", and "011".\n
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\n

Constraints:

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