2585-number-of-ways-to-earn-points.adoc

2585. Number of Ways to Earn Points

{leetcode}/problems/number-of-ways-to-earn-points/[LeetCode - 2585. Number of Ways to Earn Points ^]

There is a test that has n types of questions. You are given an integer target and a 0-indexed 2D integer array types where types[i] = [count<sub>i</sub>, marks<sub>i</sub>] indicates that there are count<sub>i</sub> questions of the ith type, and each one of them is worth marks<sub>i</sub> points.

Return the number of ways you can earn exactly _`target` points in the exam_. Since the answer may be too large, return it modulo 109 + 7.

Note that questions of the same type are indistinguishable.

• For example, if there are 3 questions of the same type, then solving the 1st and 2nd questions is the same as solving the 1st and 3rd questions, or the 2nd and 3rd questions.

Example 1:

Input: target = 6, types = [[6,1],[3,2],[2,3]]
Output: 7
Explanation: You can earn 6 points in one of the seven ways:
- Solve 6 questions of the 0th type: 1 + 1 + 1 + 1 + 1 + 1 = 6
- Solve 4 questions of the 0th type and 1 question of the 1st type: 1 + 1 + 1 + 1 + 2 = 6
- Solve 2 questions of the 0th type and 2 questions of the 1st type: 1 + 1 + 2 + 2 = 6
- Solve 3 questions of the 0th type and 1 question of the 2nd type: 1 + 1 + 1 + 3 = 6
- Solve 1 question of the 0th type, 1 question of the 1st type and 1 question of the 2nd type: 1 + 2 + 3 = 6
- Solve 3 questions of the 1st type: 2 + 2 + 2 = 6
- Solve 2 questions of the 2nd type: 3 + 3 = 6

Example 2:

Input: target = 5, types = [[50,1],[50,2],[50,5]]
Output: 4
Explanation: You can earn 5 points in one of the four ways:
- Solve 5 questions of the 0th type: 1 + 1 + 1 + 1 + 1 = 5
- Solve 3 questions of the 0th type and 1 question of the 1st type: 1 + 1 + 1 + 2 = 5
- Solve 1 questions of the 0th type and 2 questions of the 1st type: 1 + 2 + 2 = 5
- Solve 1 question of the 2nd type: 5

Example 3:

Input: target = 18, types = [[6,1],[3,2],[2,3]]
Output: 1
Explanation: You can only earn 18 points by answering all questions.

Constraints:

• 1 ⇐ target ⇐ 1000

• n == types.length

• 1 ⇐ n ⇐ 50

• types[i].length == 2

• 1 ⇐ count<sub>i</sub>, marks<sub>i</sub> ⇐ 50

思路分析

一刷

link:{sourcedir}/_2585_NumberOfWaysToEarnPoints.java[role=include]

参考资料