1043. Partition Array for Maximum Sum

本文介绍了一种基于动态规划(DP)的算法,用于解决给定数组A和整数K的最大分区求和问题。通过将数组分割成长度不超过K的连续子数组,并将每个子数组的元素替换为该子数组的最大值,目标是找到这些子数组的最大总和。文章提供了Python实现代码,包括处理边界条件和计算最优解的过程。

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Given an integer array A, you partition the array into (contiguous) subarrays of length at most K.  After partitioning, each subarray has their values changed to become the maximum value of that subarray.

Return the largest sum of the given array after partitioning.

 

Example 1:

Input: A = [1,15,7,9,2,5,10], K = 3
Output: 84
Explanation: A becomes [15,15,15,9,10,10,10]

 

Note:

  1. 1 <= K <= A.length <= 500
  2. 0 <= A[i] <= 10^6

思路:DP,

class Solution(object):
    def maxSumAfterPartitioning(self, A, K):
        """
        :type A: List[int]
        :type K: int
        :rtype: int
        """
        n=len(A)
        ma=[[0 for _ in range(n)] for _ in range(n)]
        for i in range(n):
            ma[i][i]=A[i]
            for j in range(i+1,n): ma[i][j]=max(ma[i][j-1],A[j])
        
        dp=[0 for _ in range(n)]
        dp[0]=A[0]
        for i in range(1,n):
            for j in range(1,min(K+1,i+2)):
                if i-j<0: dp[i]=max(dp[i],ma[0][i]*(i+1))
                else: dp[i]=max(dp[i],dp[i-j]+ma[i-j+1][i]*j)
        
        return dp[-1]
    

 

做前面那题做崩了,一开始连题目也看错了,各种边界也没处理好

Yousef has an array a of size n . He wants to partition the array into one or more contiguous segments such that each element ai belongs to exactly one segment. A partition is called cool if, for every segment bj , all elements in bj also appear in bj+1 (if it exists). That is, every element in a segment must also be present in the segment following it. For example, if a=[1,2,2,3,1,5] , a cool partition Yousef can make is b1=[1,2] , b2=[2,3,1,5] . This is a cool partition because every element in b1 (which are 1 and 2 ) also appears in b2 . In contrast, b1=[1,2,2] , b2=[3,1,5] is not a cool partition, since 2 appears in b1 but not in b2 . Note that after partitioning the array, you do not change the order of the segments. Also, note that if an element appears several times in some segment bj , it only needs to appear at least once in bj+1 . Your task is to help Yousef by finding the maximum number of segments that make a cool partition. Input The first line of the input contains integer t (1≤t≤104 ) — the number of test cases. The first line of each test case contains an integer n (1≤n≤2⋅105 ) — the size of the array. The second line of each test case contains n integers a1,a2,…,an (1≤ai≤n ) — the elements of the array. It is guaranteed that the sum of n over all test cases doesn't exceed 2⋅105 . Output For each test case, print one integer — the maximum number of segments that make a cool partition. Example InputCopy 8 6 1 2 2 3 1 5 8 1 2 1 3 2 1 3 2 5 5 4 3 2 1 10 5 8 7 5 8 5 7 8 10 9 3 1 2 2 9 3 3 1 4 3 2 4 1 2 6 4 5 4 5 6 4 8 1 2 1 2 1 2 1 2 OutputCopy 2 3 1 3 1 3 3 4 Note The first test case is explained in the statement. We can partition it into b1=[1,2] , b2=[2,3,1,5] . It can be shown there is no other partition with more segments. In the second test case, we can partition the array into b1=[1,2] , b2=[1,3,2] , b3=[1,3,2] . The maximum number of segments is 3 . In the third test case, the only partition we can make is b1=[5,4,3,2,1]
06-09
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