題目

在一個數組中找兩個子陣列,求其最大和(子陣列不重合,不空)

解法

從右向左遍歷，找到右邊子陣列的最大和

再從左向右遍歷，找到左邊子陣列的最大和的同時，找這兩者的最大和

兩遍 dp 即可

程式碼

def maxTwoSubStringSum(nums):
    ans = -float('inf')
    leftAns = []
    cur = 0
    
    # from right to left
    for i in range(len(nums)-1, -1, -1):
        if cur < 0:
            cur = nums[i]
        
 
else:
            cur += nums[i]
        ans = max(cur, ans)
        leftAns.append(ans)
    
    leftAns = leftAns[::-1]
    ans = -float('inf')
    rightAns = -float('inf')
    cur = 0

    # from left to right
    for i in range(len(nums)):
        if cur < 0:
            cur = nums[i]
        else
 
:
            cur += nums[i]
        rightAns = max(cur, rightAns)
        ans = max(ans, rightAns + leftAns[i])
    
    return ans


nums = [-1,2,3,4,1,-7,5,0]
print(maxTwoSubStringSum(nums))

nums = [-1,2,3,4,1,-100,5,0]
print(maxTwoSubStringSum(nums))