HTMLify

from collections import deque

class Solution:
    def kBitFlips(self, arr, k):
        n = len(arr)
        flip_ends = deque()
        total_flips = 0
        
        for i in range(n):
            if flip_ends and flip_ends[0] == i:
                flip_ends.popleft()
            
            current_flip_count = len(flip_ends)
            
            if (arr[i] + current_flip_count) % 2 == 0:
                if i + k > n:
                    return -1
                
                total_flips += 1
                flip_ends.append(i + k)
                
        return total_flips