LeetCode-in-Java

3676. Count Bowl Subarrays

Medium

You are given an integer array nums with distinct elements.

A subarray nums[l...r] of nums is called a bowl if:

• The subarray has length at least 3. That is, r - l + 1 >= 3.
• The minimum of its two ends is strictly greater than the maximum of all elements in between. That is, min(nums[l], nums[r]) > max(nums[l + 1], ..., nums[r - 1]).

Return the number of bowl subarrays in nums.

Example 1:

Input: nums = [2,5,3,1,4]

Output: 2

Explanation:

The bowl subarrays are [3, 1, 4] and [5, 3, 1, 4].

• [3, 1, 4] is a bowl because min(3, 4) = 3 > max(1) = 1.
• [5, 3, 1, 4] is a bowl because min(5, 4) = 4 > max(3, 1) = 3.

Example 2:

Input: nums = [5,1,2,3,4]

Output: 3

Explanation:

The bowl subarrays are [5, 1, 2], [5, 1, 2, 3] and [5, 1, 2, 3, 4].

Example 3:

Input: nums = [1000000000,999999999,999999998]

Output: 0

Explanation:

No subarray is a bowl.

Constraints:

• 3 <= nums.length <= 105
• 1 <= nums[i] <= 109
• nums consists of distinct elements.

Solution

public class Solution {
    public long bowlSubarrays(int[] nums) {
        int n = nums.length;
        int res = n;
        int pre = 0;
        for (int a : nums) {
            if (a > pre) {
                res--;
                pre = a;
            }
        }
        pre = 0;
        for (int i = n - 1; i >= 0; i--) {
            if (nums[i] > pre) {
                res--;
                pre = nums[i];
            }
        }
        return res + 1L;
    }
}