2140.Solving Questions With Brainpower

tags: `Medium`,`Array`,`DP`

題目描述

You are given a 0-indexed 2D integer array questions where questions[i] = [

p o i n t s_{i}

b r a i n p o w e r_{i}

The array describes the questions of an exam, where you have to process the questions in order (i.e., starting from question 0) and make a decision whether to solve or skip each question. Solving question i will earn you

p o i n t s_{i}

points but you will be unable to solve each of the next

b r a i n p o w e r_{i}

questions. If you skip question i, you get to make the decision on the next question.

For example, given questions = [[3, 2], [4, 3], [4, 4], [2, 5]]:
- If question 0 is solved, you will earn 3 points but you will be unable to solve questions 1 and 2.
- If instead, question 0 is skipped and question 1 is solved, you will earn 4 points but you will be unable to solve questions 2 and 3.

Return the maximum points you can earn for the exam.

範例

Example 1:

Input: questions = [[3,2],[4,3],[4,4],[2,5]]
Output: 5
Explanation: The maximum points can be earned by solving questions 0 and 3.
- Solve question 0: Earn 3 points, will be unable to solve the next 2 questions
- Unable to solve questions 1 and 2
- Solve question 3: Earn 2 points
Total points earned: 3 + 2 = 5. There is no other way to earn 5 or more points.

Example 2:

Input: questions = [[1,1],[2,2],[3,3],[4,4],[5,5]]
Output: 7
Explanation: The maximum points can be earned by solving questions 1 and 4.
- Skip question 0
- Solve question 1: Earn 2 points, will be unable to solve the next 2 questions
- Unable to solve questions 2 and 3
- Solve question 4: Earn 5 points
Total points earned: 2 + 5 = 7. There is no other way to earn 7 or more points.

Constraints:

1 <= questions.length <= 10⁵
questions[i].length == 2
1 <=
$p o i n t s_{i}$ ,
$b r a i n p o w e r_{i}$ <= 10⁵

解答

Javascript















function mostPoints(questions) {
  const n = questions.length - 1;
  const dp = new Array(n).fill(0);
  dp[n] = questions[n][0];
  for (let i = n - 1; i >= 0; i--) {
    const [point, brainpower] = questions[i];
    if (i + brainpower + 1 > n) {
      dp[i] = Math.max(dp[i + 1], point);
    } else {
      dp[i] = Math.max(dp[i + 1], dp[i + brainpower + 1] + point);
    }
  }

  return dp[0];
}

第一次錯是沒注意到brainpower應該要從後面往回看才對
第二次錯是沒注意到brainpower要+1
不過這個跑測試就發現了應該不算錯吧ㄏㄏ

MarsgoatMay 12, 2023

Python













class Solution:
    def mostPoints(self, questions: List[List[int]]) -> int:
        n = len(questions)
        dp = [0] * n
        dp[-1] = questions[-1][0]

        for i in range(n - 2, -1, -1):
            dp[i], skip = questions[i]
            if i + skip + 1 < n:
                dp[i] += dp[i + skip + 1]
            dp[i] = max(dp[i], dp[i + 1])
        
        return dp[0]

Yen-Chi ChenFri, May 12, 2023

C#















public long MostPoints(int[][] questions) {
    int size = questions.Length;
    long[] points = new long[size];
    points[^1] = questions[^1][0];

    for (int i = size - 2; i >= 0; i--) {
        points[i] = questions[i][0];
        int skipedIndex = i + questions[i][1] + 1;
        if (skipedIndex < size) {
            points[i] += points[skipedIndex];
        }
        points[i] = Math.Max(points[i], points[i + 1]);
    }
    return points[0];
}

JimMay 13, 2023

Reference

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