2466-count-ways-to-build-good-strings.adoc

2466. Count Ways To Build Good Strings

{leetcode}/problems/count-ways-to-build-good-strings/[LeetCode - 2466. 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:

• Append the character '0' zero times.

• Append the character '1' one times.

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 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".

Constraints:

• 1 ⇐ low ⇐ high ⇐ 105

• 1 ⇐ zero, one ⇐ low

思路分析

一刷

link:{sourcedir}/_2466_CountWaysToBuildGoodStrings.java[role=include]

参考资料