In an array A containing only 0s and 1s, a K-bit flip consists of choosing a (contiguous) subarray of length K and simultaneously changing every 0 in the subarray to 1, and every 1 in the subarray to 0.
Return the minimum number of K-bit flips required so that there is no 0 in the array. If it is not possible, return -1.
Example 1:
Input: A = [0,1,0], K = 1 Output: 2 Explanation: Flip A[0], then flip A[2].
Example 2:
Input: A = [1,1,0], K = 2 Output: -1 Explanation: No matter how we flip subarrays of size 2, we can't make the array become [1,1,1].
Example 3:
Input: A = [0,0,0,1,0,1,1,0], K = 3 Output: 3 Explanation: Flip A[0],A[1],A[2]: A becomes [1,1,1,1,0,1,1,0] Flip A[4],A[5],A[6]: A becomes [1,1,1,1,1,0,0,0] Flip A[5],A[6],A[7]: A becomes [1,1,1,1,1,1,1,1]
Note:
1 <= A.length <= 300001 <= K <= A.length
[Greedy] [Sliding Window]
- Bulb Switcher (Medium)