#2719
Count of Integers
hard · verified · 38.2% accepted · 571 likes · top 17%
math · string · dynamic programming
Description
You are given two numeric strings num1 and num2 and two integers max_sum and min_sum. We denote an integer x to be good if:
- num1 <= x <= num2
- min_sum <= digit_sum(x) <= max_sum.
Return the number of good integers. Since the answer may be large, return it modulo 109 + 7.
Note that digit_sum(x) denotes the sum of the digits of x.
Example 1:
Input: num1 = "1", num2 = "12", min_sum = 1, max_sum = 8
Output: 11
Explanation: There are 11 integers whose sum of digits lies between 1 and 8 are 1,2,3,4,5,6,7,8,10,11, and 12. Thus, we return 11.
Example 2:
Input: num1 = "1", num2 = "5", min_sum = 1, max_sum = 5
Output: 5
Explanation: The 5 integers whose sum of digits lies between 1 and 5 are 1,2,3,4, and 5. Thus, we return 5.
Solution