Number of Good Binary Strings

You are given four integers minLength, maxLength, oneGroup and zeroGroup.

A binary string is good if it satisfies the following conditions:

• The length of the string is in the range [minLength, maxLength].
• The size of each block of consecutive 1's is a multiple of oneGroup.
  • For example in a binary string 00110111100 sizes of each block of consecutive ones are [2,4].
• The size of each block of consecutive 0's is a multiple of zeroGroup.
  • For example, in a binary string 00110111100 sizes of each block of consecutive ones are [2,1,2].

Return the number of good binary strings. Since the answer may be too large, return it modulo 109 + 7.

Note that 0 is considered a multiple of all the numbers.

 

Example 1:

Input: minLength = 2, maxLength = 3, oneGroup = 1, zeroGroup = 2
Output: 5
Explanation: There are 5 good binary strings in this example: "00", "11", "001", "100", and "111".
It can be proven that there are only 5 good strings satisfying all conditions.

Example 2:

Input: minLength = 4, maxLength = 4, oneGroup = 4, zeroGroup = 3
Output: 1
Explanation: There is only 1 good binary string in this example: "1111".
It can be proven that there is only 1 good string satisfying all conditions.

 

Constraints:

• 1 <= minLength <= maxLength <= 105
• 1 <= oneGroup, zeroGroup <= maxLength