795. Number of Subarrays with Bounded Maximum

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We are given an array A of positive integers, and two positive integers L and R (L <= R).

Return the number of (contiguous, non-empty) subarrays such that the value of the maximum array element in that subarray is at least L and at most R.

Example :
Input: 
A = [2, 1, 4, 3]
L = 2
R = 3
Output: 3
Explanation: There are three subarrays that meet the requirements: [2], [2, 1], [3].

Note:

• L, R  and A[i] will be an integer in the range [0, 10^9].
• The length of A will be in the range of [1, 50000].

程序如下所示：

class Solution {
    public int numSubarrayBoundedMax(int[] A, int L, int R) {
        int res = 0;
        int pre = -1, cur = -1;
        for (int i = 0; i < A.length; ++ i){
            if (A[i] > R){
                pre = cur = i;
                continue;
            }
            if (A[i] >= L){
                cur = i;
            }
            res += cur - pre;
        }
        return res;
    }
}