Find the Original Typed String II
Alice is attempting to type a specific string on her computer.
Alice is attempting to type a specific string on her computer. However, she tends to be clumsy and may press a key for too long, resulting in a character being typed multiple times.
You are given a string word, which represents the final output displayed on Alice's screen. You are also given a positive integer k.
Return the total number of possible original strings that Alice might have intended to type, if she was trying to type a string of size at least k.
Since the answer may be very large, return it modulo 10^9 + 7.
Example 1
Input: word = "aabbccdd", k = 7
Output: 5
Explanation: The possible strings are: "aabbccdd" , "aabbccd" , "aabbcdd" , "aabccdd" , and "abbccdd" .
Example 2
Input: word = "aabbccdd", k = 8
Output: 1
Explanation: The only possible string is "aabbccdd" .
Example 3
Input: word = "aaabbb", k = 3
Output: 8
Constraints
- 1 <= word.length <= 5 * 10^5
- word consists only of lowercase English letters.
- 1 <= k <= 2000
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