1004. Max Consecutive Ones III

Given an array A of 0s and 1s, we may change up to K values from 0 to 1.

Return the length of the longest (contiguous) subarray that contains only 1s.

Example 1:

Input: A = [1,1,1,0,0,0,1,1,1,1,0], K = 2
Output: 6
Explanation: 
[1,1,1,0,0,1,1,1,1,1,1]
Bolded numbers were flipped from 0 to 1.  The longest subarray is underlined.

Example 2:

Input: A = [0,0,1,1,0,0,1,1,1,0,1,1,0,0,0,1,1,1,1], K = 3
Output: 10
Explanation: 
[0,0,1,1,1,1,1,1,1,1,1,1,0,0,0,1,1,1,1]
Bolded numbers were flipped from 0 to 1.  The longest subarray is underlined.

Note:

1. 1 <= A.length <= 20000

2. 0 <= K <= A.length

3. A[i] is 0 or 1

// Sliding window
int longestOnes(vector<int>& A, int K) { // time: O(n); space: O(1)
    int res = 0, zero_cnt = 0, begin = 0, end = 0;
    while (end < A.size()) {
        if (A[end++] == 0) ++zero_cnt;
        if (zero_cnt > K && A[begin++] == 0) --zero_cnt;
        res = max(res, end - begin);
    }
    return res;
}

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