Flip Consecutive Zeroes to Ones in K Operations: A Step-by-Step Guide to Maximizing Ones
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Flip Consecutive Zeroes to Ones in K Operations: A Step-by-Step Guide to Maximizing Ones

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Welcome to this comprehensive guide on how to flip consecutive zeroes to ones in K operations to achieve the maximum number of ones. This problem is a classic example of a dynamic programming challenge, and we’ll break it down into manageable chunks to help you understand and solve it efficiently.

Problem Statement

Given a binary array consisting of zeroes and ones, you are allowed to perform K operations. In each operation, you can flip a sequence of consecutive zeroes to ones. The goal is to maximize the number of ones in the array after performing K operations.

Example

Suppose we have the following binary array: [0, 0, 1, 0, 0, 1, 0, 0] and K = 3 operations. After performing three operations, we can get the maximum number of ones as follows:

Initial array: [0, 0, 1, 0, 0, 1, 0, 0]
Operation 1: Flip [0, 0] to [1, 1] -> [1, 1, 1, 0, 0, 1, 0, 0]
Operation 2: Flip [0, 0] to [1, 1] -> [1, 1, 1, 1, 1, 1, 0, 0]
Operation 3: Flip [0, 0] to [1, 1] -> [1, 1, 1, 1, 1, 1, 1, 1]

In this example, we’ve maximized the number of ones to 8.

Approach

To solve this problem, we’ll use dynamic programming to build a solution from smaller subproblems. We’ll create a 2D table, dp, where dp[i][k] represents the maximum number of ones we can get after performing k operations on the first i elements of the array.

State Transition

The state transition can be defined as follows:

dp[i][k] = max(dp[i-1][k], dp[i-1][k-1] + 1)

Here, we have two choices:

  • Not flip the current element: We take the maximum number of ones from the previous element, i.e., dp[i-1][k].
  • Flip the current element: We take the maximum number of ones from the previous element after performing one operation, i.e., dp[i-1][k-1] + 1.

Algorithm

Here’s the step-by-step algorithm to solve the problem:

  1. Create a 2D table, dp, of size (n x K+1), where n is the length of the input array.

Code Implementation

def max_ones(arr, K):
    n = len(arr)
    dp = [[0] * (K + 1) for _ in range(n + 1)]

    for k in range(1, K + 1):
        dp[0][k] = -1

    for i in range(1, n + 1):
        for k in range(1, K + 1):
            if arr[i - 1] == 0:
                dp[i][k] = max(dp[i - 1][k], dp[i - 1][k - 1] + 1)
            else:
                dp[i][k] = max(dp[i - 1][k], dp[i - 1][k])

    return dp[n][K]

Time and Space Complexity

The time complexity of this algorithm is O(nK), where n is the length of the input array and K is the number of operations. The space complexity is O(nK) as well, since we need to store the 2D table dp.

Optimization Techniques

To optimize the solution, we can use the following techniques:

  • Memoization: Store the intermediate results in a cache to avoid re-computing them.
  • Bottom-up Dynamic Programming: Build the solution from smaller subproblems to avoid redundant computations.
  • Pruning: Remove unnecessary states from the DP table to reduce the space complexity.

Conclusion

In this article, we’ve discussed a step-by-step approach to flip consecutive zeroes to ones in K operations to maximize the number of ones in a binary array. We’ve covered the problem statement, example, approach, algorithm, code implementation, time and space complexity, and optimization techniques. By applying dynamic programming and optimization techniques, we can efficiently solve this problem and achieve the maximum number of ones.

Keyword Frequency
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Frequently Asked Questions

Get ready to flip your way to a maximum number of ones in k operations!

What is the problem all about?

Given a binary array and an integer k, you need to flip consecutive zeroes to ones in k operations to have a maximum number of ones. The goal is to find the maximum number of ones that can be achieved.

How do I approach this problem?

To solve this problem, you can use a sliding window approach. Initialize two pointers, left and right, to the start of the array. Then, try to extend the window to the right as much as possible while keeping the number of zeroes in the window less than or equal to k. Update the maximum number of ones accordingly.

What is the time complexity of this approach?

The time complexity of the sliding window approach is O(n), where n is the length of the binary array. This is because we only need to traverse the array once to find the maximum number of ones.

Can I use a greedy approach to solve this problem?

Yes, a greedy approach can also be used to solve this problem. The idea is to always flip the leftmost k zeroes to ones, which will give you the maximum number of ones. However, this approach is less efficient than the sliding window approach, with a time complexity of O(nk).

What if the input array is very large?

If the input array is very large, the sliding window approach is still efficient and can handle it. However, if k is also very large, the greedy approach might be more suitable. Alternatively, you can use a more efficient algorithm or data structure, such as a binary indexed tree, to solve the problem.

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