995

class Solution {
public:
    int minKBitFlips(vector<int>& A, int K) {
        int ans, flip, n = A.size();
        int close[n];
        memset(close, 0, sizeof(close));

        ans = flip = 0;
        for(int i=0; i<n; i++){
            flip ^= close[i];
            if(A[i] == flip){
                ans++;
                if(i+K > n) return -1;
                flip ^= 1;
                if(i+K < n) close[i+K] ^= 1;
            }
        }
        return ans;
    }
};