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Flip Bits
Easy Accuracy: 39.03% Submissions: 2594 Points: 2

Given an array A[] consisting of 0’s and 1’s. A flip operation is one in which you turn 1 into 0 and a 0 into 1. You have to do at most one “Flip” operation of any subarray. Formally, select a range (l, r) in the array A[], such that (0 ≤ l ≤ r < n) holds and flip the elements in this range to get the maximum ones in the final array. You can possibly make zero operations to get the answer.

Example 1:

Input:
N = 5
A[] = {1, 0, 0, 1, 0}
Output:
4
Explanation:
We can perform a flip operation in the range [1,2]
After flip operation array is : [ 1 1 1 1 0 ]
Count of one after fliping is : 4
[Note: the subarray marked in bold is the flipped subarray]

Example 2:

Input:
N = 7
A[] = {1, 0, 0, 1, 0, 0, 1}
Output:
6
Explanation:
We can perform a flip operation in the range [1,5]
After flip operation array is : [ 1 1 1 0 1 1 1]
Count of one after fliping is : 6
[Note: the subarray marked in bold is the flipped subarray]

You don't need to read input or print anything. Your task is to complete the function maxOnes() which takes the array A[] and its size N as inputs and returns the maximum number of 1's you can have in the array after atmost one flip operation.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(1)

Constraints:
1 ≤ N ≤ 104
0 ≤ A[i] ≤ 1