Question

我创建了一个递归函数，它接受一个int数组，并返回具有最大总和的连续子数组的总和。

示例：

输入：1 4 -9 8 1 3 3 1 -1 -4 -6 2 8 19 -10 -11

子阵列：8 1 3 3 1 -1 -4 -6 2 8 19

总和：34

我的算法有点偏。大约2/3的测试输入是错误的。我的测试列表在代码下面。

def max_sum_subarray(arr, left, right):

    maxLeftBorderSum = 0
    maxRightBorderSum = 0
    leftBorderSum = 0
    rightBorderSum = 0
    center = (left + right)/2

    if left == right:
        return arr[left]

    maxLeftSum = min_sum_subarray(arr, left, center)
    maxRightSum = min_sum_subarray(arr, center+1, right)

    for i in range(center, left, -1):
        leftBorderSum = leftBorderSum + arr[i]
        if leftBorderSum > maxLeftBorderSum:
            maxLeftBorderSum = leftBorderSum

    for i in range(center+1, right):
        rightBorderSum = rightBorderSum + arr[i]
        if rightBorderSum > maxRightBorderSum:
            maxRightBorderSum = rightBorderSum  

    return max(maxLeftBorderSum + maxRightBorderSum, max(maxRightSum, maxLeftSum))

一些测试：

1 4 -9 8 1 3 3 1 -1 -4 -6 2 8 19 -10 -11

正确答案= 34
我的回答= 34

2 9 8 6 5 -11 9 -11 7 5 -1 -8 -3 7 -2

正确答案= 30
我的回答= 28

10 -11 -1 -9 33 -45 23 24 -1 -7 -8 19

正确答案= 50
我的回答= 47

31 -41 59 26 -53 58 97 -93 -23 84

正确答案= 187
我的答案= 187

3 2 1 1 -8 1 1 2 3

正确答案= 7
我的回答= 4

12 99 99 -99 -27 0 0 0 -3 10

正确答案= 210
我的回答= 198

-2 1 -3 4 -1 2 1 -5 4

正确答案= 6
我的回答= 6

Answer 1

Diffchecker

#!python3
def max_sum_subarray(arr, left, right):

maxLeftBorderSum = 0
maxRightBorderSum = 0
leftBorderSum = 0
rightBorderSum = 0
center = (left + right)//2

if left == right:
    if(arr[left]>0):return arr[left]
    else:return 0

maxLeftSum = max_sum_subarray(arr, left, center)
maxRightSum = max_sum_subarray(arr, center+1, right)

for i in range(center, left-1, -1):
    leftBorderSum = leftBorderSum + arr[i]
    if leftBorderSum > maxLeftBorderSum:
        maxLeftBorderSum = leftBorderSum
for i in range(center+1, right+1):
    rightBorderSum = rightBorderSum + arr[i]
    if rightBorderSum > maxRightBorderSum:
        maxRightBorderSum = rightBorderSum  

return max(maxLeftBorderSum + maxRightBorderSum,maxRightSum, maxLeftSum)

基本条件错误
for loop range wrong
调用错误的功能
如果python3使用true division

Answer 2

import sys 
arr = map(int,raw_input().split())
def CrossingSum(arr,l,m,h):
    summ = 0
    left_sum = -sys.maxint
    for i in range(m,l-1,-1):

            summ = summ + arr[i]
            if summ > left_sum:
                    left_sum = summ


    summ = 0
    right_sum = -sys.maxint
    for i in range(m+1,h+1):
            summ = summ + arr[i]
            if summ > right_sum:
                    right_sum = summ

    return left_sum + right_sum

def Divide(arr,l,h):
    if l ==  h :
            return arr[l]
    mid = (l+h)//2
    maximum = max(Divide(arr,l,mid) , Divide(arr,mid+1,h) , CrossingSum(arr,l,mid,h))

    return maximum

ans = Divide(arr,0,len(arr)-1)
print "ANSWER IS " , ans

Max Sum Subarray - 分而治之

2 个答案: