Find Indexs of 0 to be replaced with 1 to get longest continuous sequence of 1s in a binary array - Set-2 in Python

Suppose we have one binary array. We have to find the position of 0 that can be replaced with 1 to get maximum number of continuous sequence of 1s.

So, if the input is like [1, 1, 0, 0, 1, 0, 1, 1, 1, 1, 0, 1, 1], then the output will be 10, so the array will be [1, 1, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1].

To solve this, we will follow these steps −

• i := 0,

• n := size of A

• count_left := 0, count_right := 0

• max_i := -1, last_i := -1

• count_max := 0

• while i < n, do

  • if A[i] is same as 1, then

    • count_right := count_right + 1

  • otherwise,

    • if last_i is not same as -1, then

      • if count_right + count_left + 1 > count_max, then

        • count_max := count_left + count_right + 1

        • max_i := last_i

    • last_i := i

    • count_left := count_right

    • count_right := 0

  • i := i + 1

• if last_i is not same as -1, then

  • if count_left + count_right + 1 > count_max, then

    • count_max := count_left + count_right + 1

    • max_i := last_i

• return max_i

Example

Let us see the following implementation to get better understanding −

def find_max_one_index(A):
   i = 0
   n = len(A)
   count_left = 0
   count_right = 0
   max_i = -1
   last_i = -1
   count_max = 0
   while i < n:
      if A[i] == 1:
         count_right += 1
      else:
         if last_i != -1:
            if count_right + count_left + 1 > count_max:
               count_max = count_left + count_right + 1
               max_i = last_i
            last_i = i
            count_left = count_right
            count_right = 0
      i += 1
   if last_i != -1:
      if count_left + count_right + 1 > count_max:
         count_max = count_left + count_right + 1
         max_i = last_i
   return max_i
A = [1, 1, 0, 0, 1, 0, 1, 1, 1, 1, 0, 1, 1]
print(find_max_one_index(A))

Input

[1, 1, 0, 0, 1, 0, 1, 1, 1, 1, 0, 1, 1]

Output

10