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.

分析：
用两个指针: start, end. 不断往前移动end，当arr[end]是0的话，count--。如果count < 0，那么就往前移动start, 然后不断比较global_max和 end - start + 1. 

class Solution {
    public int longestOnes(int[] nums, int k) {
        int max = 0, start = 0;
        for (int end = 0; end < nums.length; end++) {
            if (nums[end] == 0) {
                k--;
            }
            while (k < 0) {
                if (nums[start] == 0) {
                    k++;
                }
                start++;
            }
            max = Integer.max(max, end - start + 1);
        }
        return max;
    }
}