leetcode

0995.cpp (482B)

 class Solution {
   public:
     int minKBitFlips(vector<int> &nums, int k) const {
         const int n = size(nums);
         int res = 0, flips = 0;
 
         for (int i = 0; i < n; i++) {
             if (nums[i] == flips % 2) {
                 if (i > n - k) return -1;
                 nums[i] -= 2, res++, flips++;
             }
 
             const int prev = i - k + 1;
             if (i >= k - 1 && nums[prev] < 0) nums[prev] += 2, flips--;
         }
 
         return res;
     }
 };