The score of an array is defined as the product of its sum and its length.
[1, 2, 3, 4, 5] is (1 + 2 + 3 + 4 + 5) * 5 = 75.Given a positive integer array nums and an integer k, return the number of non-empty subarrays of nums whose score is strictly less than k.
A subarray is a contiguous sequence of elements within an array.
Example 1:
Input: nums = [2,1,4,3,5], k = 10 Output: 6 Explanation: The 6 subarrays having scores less than 10 are: - [2] with score 2 * 1 = 2. - [1] with score 1 * 1 = 1. - [4] with score 4 * 1 = 4. - [3] with score 3 * 1 = 3. - [5] with score 5 * 1 = 5. - [2,1] with score (2 + 1) * 2 = 6. Note that subarrays such as [1,4] and [4,3,5] are not considered because their scores are 10 and 36 respectively, while we need scores strictly less than 10.
Example 2:
Input: nums = [1,1,1], k = 5 Output: 5 Explanation: Every subarray except [1,1,1] has a score less than 5. [1,1,1] has a score (1 + 1 + 1) * 3 = 9, which is greater than 5. Thus, there are 5 subarrays having scores less than 5.
Constraints:
1 <= nums.length <= 1051 <= nums[i] <= 1051 <= k <= 1015class Solution {
public long countSubarrays(int[] nums, long k) {
long prefixSum = 0, ans = 0;
for (int lt = 0, rt = 0; rt < nums.length; rt++) {
prefixSum += nums[rt];
while (lt <= rt && prefixSum * (rt - lt + 1) >= k)
prefixSum -= nums[lt++];
ans += rt - lt + 1;
}
return ans;
}
}