1004. Max Consecutive Ones III - Medium

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

time = O(n), space = O(1)

class Solution {
    public int longestOnes(int[] A, int K) {
        if(A == null || A.length == 0) {
            return 0;
        }
        int s = 0, f = 0, numOfZero = 0, max = 0;
        while(f < A.length) {
            if(A[f++] == 0) {
                numOfZero++;
            }
            while(numOfZero > K) {
                if(A[s++] == 0) {
                    numOfZero--;
                }
            }
            max = Math.max(max, f - s);
        }
        return max;
    }
}