Leetcode-995 Minimum Number of K Consecutive Bit Flips(K 连续位的最小翻转次数)

#define maxn 30002
#define _for(i,a,b) for(int i = (a);i < (b);i ++)
int dir[maxn],f[maxn],n;
class Solution
{
    public:
        int solve(int k)
        {
            memset(f,0,sizeof(f));
            int sum=0,res=0;
            for(int i=0; i+k<=n; i++)
            {
                if((dir[i] + sum) %2== 1)
                {
                    f[i]=1;
                    res++;
                }
                sum+=f[i];
                if(i-k+1>=0) sum-=f[i-k+1];
            }
            
            for(int i=n-k+1; i<n; i++) 
            {
                if((dir[i] + sum) %2== 1) return -1;
                if(i-k+1>=0) sum-=f[i-k+1];
            }
            return res;
        }

        int minKBitFlips(vector<int>& A, int K)
        {
            n = A.size();
            _for(i,0,n)
                if(A[i])
                    dir[i] = 0;
                else
                    dir[i] = 1;
            return solve(K);
        }
};

经典ACM问题——奶牛掉头