Program to find maximum absolute sum of any subarray in Python

Suppose we have an array called nums. We have to find the absolute sum of a subarray [nums_l, nums_l+1, ..., nums_r-1, nums_r] is |nums_l + nums_l+1 + ... + nums_r-1 + nums_r|. We have to find the maximum absolute sum of any subarray of nums (that subarray can possibly be empty).

So, if the input is like nums = [2,-4,-3,2,-6], then the output will be 11 because the subarray [2,-4,-3,2] has maximum absolute subarray sum |2 + (-4) + (-3) + 2| = 11.

To solve this, we will follow these steps −

• n:= size of nums

• ans:= 0, temp:= 0

• for i in range 0 to n - 1, do

  • if temp < 0, then

    • temp:= 0

  • temp:= temp + nums[i]

  • ans:= maximum of ans and |temp|

• temp:= 0

• for i in range 0 to n - 1, do

  • if temp > 0, then

    • temp:= 0

  • temp:= temp + nums[i]

  • ans:= maximum of ans and |temp|

• return ans

Example

Let us see the following implementation to get better understanding −

def solve(nums):
   n=len(nums)
   ans=0
   temp=0

   for i in range(n):
      if (temp<0):
         temp=0
   temp=temp+nums[i]
   ans=max(ans,abs(temp))

   temp=0
   for i in range(n):
      if (temp>0):
         temp=0
      temp=temp+nums[i]
      ans=max(ans,abs(temp))

   return ans

nums = [2,-4,-3,2,-6]
print(solve(nums))

Input

[2,-4,-3,2,-6]

Output

11