#688 · #2466 · Count Ways To Build Good Strings(统计构造好字符串的方案数)

Given low, high, zero, and one, build strings by appending either zero copies of the character zero or one copies of the character one at a time. A good string has length in the inclusive range [low, high]. Return the number of distinct good strings modulo 10^9 + 7. Constraints: 1 <= low <= high <= 10^5, 1 <= zero, one <= 10^5.