Syntax error Program to find maximum length of subarray with positive product in Python

Program to find maximum length of subarray with positive product in Python

Suppose we have an array called nums, we have to find the maximum length of a subarray where the product of all its elements is positive. We have to find the maximum length of a subarray with positive product.

So, if the input is like nums = [2,-2,-4,5,-3], then the output will be 4 because first four elements are forming a subarray whose product is positive.

To solve this, we will follow these steps :

  • Define a function util() . This will take s, e
  • neg := 0
  • ns := -1, ne := -1
  • for i in range s to e, do
    • if nums[i] < 0, then
      • neg := neg + 1
      • if ns is same as -1, then
        • ns := i
      • ne := i
  • if neg is even, then
    • return e-s+1
  • otherwise,
    • return maximum of e-ns and ne-s
  • From the main method, do the following −
  • ans := 0
  • s := -1, e := -1
  • for i in range 0 to size of nums, do
    • if nums[i] is not same as 0 and s is same as -1, then
      • s := i
    • otherwise when nums[i] is same as 0 and s is not same as -1, then
      • e := i-1
      • ans := maximum of ans and util(s, e)
      • s := -1, e := -1
  • if s is not same as -1 and e is same as -1, then
    • e := size of nums -1
    • ans := maximum of ans and util(s, e)
  • return ans

Let us see the following implementation to get better understanding:

Example

def util(s, e):
   neg = 0
   ns, ne = -1, -1
   for i in range(s, e+1):
      if nums[i]<0:
         neg += 1
         if ns == -1:
            ns = i
         ne = i

   if neg == 0 or neg %2 == 0:
      return e-s+1
   else:
      return max(e-ns, ne-s)

def solve(nums):
   ans = 0
   s, e = -1, -1

   for i in range(len(nums)):
      if nums[i]!=0 and s == -1:
         s = i
      elif nums[i]==0 and s != -1:
         e = i-1
         ans = max(ans, util(s, e))
         s = -1
         e = -1

   if s!= -1 and e == -1:
      e = len(nums)-1
      ans = max(ans, util(s, e))
      return ans

nums = [2,-2,-4,5,-3]
print(solve(nums))

Input

[2,-2,-4,5,-3]

Output

4
Updated on: 2021-10-04T07:47:16+05:30

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