Count Ways To Build Good Strings
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: This can be...
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:
This can be performed any number of times.
A good string is a string constructed by the above process having a length between low and high (inclusive).
Return the number of different good strings that can be constructed satisfying these properties. Since the answer can be large, return it modulo 10^9 + 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".
Constraints
- 1 <= low <= high <= 10^5
- 1 <= zero, one <= low
Hints
Companies
No companies reported yet.
Discussion
Sign in to join the discussion.
Loading discussion...
Test results
No test cases yet.