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Codility 9.2 MaxSliceSum [Maximu

Codility 9.2 MaxSliceSum [Maximu

作者: 波洛的汽车电子世界 | 来源:发表于2019-08-18 22:03 被阅读0次

find a maximum sum of a compact subsequence of array elements.

Task description
A non-empty array A consisting of N integers is given. A pair of integers (P, Q), such that 0 ≤ P ≤ Q < N, is called a slice of array A. The sum of a slice (P, Q) is the total of A[P] + A[P+1] + ... + A[Q].

Write a function:

def solution(A)

that, given an array A consisting of N integers, returns the maximum sum of any slice of A.

For example, given array A such that:

A[0] = 3  A[1] = 2  A[2] = -6
A[3] = 4  A[4] = 0
the function should return 5 because:

(3, 4) is a slice of A that has sum 4,
(2, 2) is a slice of A that has sum −6,
(0, 1) is a slice of A that has sum 5,
no other slice of A has sum greater than (0, 1).
Write an efficient algorithm for the following assumptions:

N is an integer within the range [1..1,000,000];
each element of array A is an integer within the range [−1,000,000..1,000,000];
the result will be an integer within the range [−2,147,483,648..2,147,483,647].

思路:我们计算到每个位置的最大和。假设在第i元素有最大的和max_ending。那么在i+1时,最大的和= max{a_{i+1}, max_ending+a_{i+1}}。max_slice存储最大值。

def solution(A):
    # write your code in Python 3.6
    max_slice = A[0]
    max_ending = 0
    
    
    #在i有最大值
    
    for i in A:
        max_ending = max(i,max_ending + i)
        max_slice = max(max_slice,max_ending)
    return max_slice

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