## 题目描述：

LeetCode 795. Number of Subarrays with Bounded Maximum

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].

## Python代码：

class Solution(object):
def numSubarrayBoundedMax(self, A, L, R):
"""
:type A: List[int]
:type L: int
:type R: int
:rtype: int
"""
ans = lastIdx = 0
for i, x in enumerate(A + [10**10]):
if x > R:
ans += self.numSubarrayMinimumMax(A[lastIdx:i], L)
lastIdx = i + 1
return ans

def numSubarrayMinimumMax(self, A, L):
"""
:type A: List[int]
:type L: int
:rtype: int
"""
ans = lastIdx = 0
for i, x in enumerate(A):
if x >= L:
ans += (i - lastIdx + 1) * (len(A) - i)
lastIdx = i + 1
return ans

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