## Description

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].
```

## Solutions

这个解法没看懂……：

```
class Solution(object):
def numSubarrayBoundedMax(self, A, L, R):
"""
:type A: List[int]
:type L: int
:type R: int
:rtype: int
"""
res = 0
left = right = -1
for i in range(len(A)):
if A[i] >= L:
right = i
if A[i] > R:
left = i
res += (right - left)
return res
# Runtime: 304 ms, faster than 81.41% of Python online submissions for Number of Subarrays with Bounded Maximum.
# Memory Usage: 14.1 MB, less than 45.45% of Python online submissions for Number of Subarrays with Bounded Maximum.
```

动规似乎好懂一些：

```
class Solution(object):
def numSubarrayBoundedMax(self, A, L, R):
"""
:type A: List[int]
:type L: int
:type R: int
:rtype: int
"""
res, dp = 0, 0
prev = -1
for i in range(len(A)):
if A[i] < L:
res += dp
if A[i] > R:
dp = 0
prev = i
if L <= A[i] <= R:
dp = i - prev
res += dp
return res
# Runtime: 304 ms, faster than 81.41% of Python online submissions for Number of Subarrays with Bounded Maximum.
# Memory Usage: 14.4 MB, less than 18.18% of Python online submissions for Number of Subarrays with Bounded Maximum.
```