Problem Statement |
| | A positive integer is called a cool number of power A if it can be separated into exactly A groups of consecutive digits, where the digits in each group form an arithmetic progression. An arithmetic progression is a sequence of numbers in which the difference between any two consecutive numbers is the same. A positive integer is called a mega cool number of power A if it is a cool number of power A, not a cool number of power A-1, and all its digits are in non-decreasing order.
Determine the number of mega cool numbers of power A that contain exactly N digits (with no leading zeroes). Return this number modulo 1,000,000,007. |
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Definition |
| | | Class: | MegaCoolNumbers | | Method: | count | | Parameters: | int, int | | Returns: | int | | Method signature: | int count(int N, int A) | | (be sure your method is public) |
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Constraints |
| - | A and N will be between 1 and 1,000, inclusive.
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Examples |
| 0) | |
| | | Returns: 9 | | There 9 such numbers: 1, 2, 3, 4, 5, 6, 7, 8, 9. |
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| 1) | |
| | | Returns: 45 | | Any two-digit number with non-decreasing digits will be a mega cool number of power 1. |
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| 2) | |
| | | Returns: 0 | | There are no such numbers. |
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| 3) | |
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