optimization version of available solution: reduce the number of times to use min()

```
def minSubArrayLen(self, s, nums):
"""
:type s: int
:type nums: List[int]
:rtype: int
"""
if((not nums) or s < 1):
return 0
min_len = len(nums) + 1
cur_sum = 0
j = 0
for i in xrange(len(nums)):
cur_sum += nums[i]
if(cur_sum < s):
continue
while(cur_sum >= s):
cur_sum -= nums[j]
j += 1
min_len = min(min_len, i - j + 2)
return min_len if min_len < len(nums) + 1 else 0
```