<双指针问题>全是正数的数组累加和为k的最长子数组长度

public static int longestSubArrayInPosArrary(int[] arr, int aim){
    if (arr == null || arr.length ==0 || aim <= 0) return 0;
    int left = 0;
    int right = 0;
    int sum = arr[0];
    int res = 0;
    while (right < arr.length) {
        if (sum == aim){
            res = Math.max(res, right - left + 1);
            right++;
            if ( right == arr.length) break;
            sum += arr[right];
        }else if (sum < aim){
            right ++;
            if ( right == arr.length) break;
            sum += arr[right];
        }else {
            sum -= arr[left];
            left++;
        }
    }
    return res;
}