```
class NumArray(object):
def __init__(self, nums):
"""
initialize your data structure here.
:type nums: List[int]
"""
self.nums = list(nums)
for i in range(1,len(nums)):
nums[i] += nums[i-1]
self.numsSum = nums
def sumRange(self, i, j):
"""
sum of elements nums[i..j], inclusive.
:type i: int
:type j: int
:rtype: int
"""
return self.numsSum[j]-self.numsSum[i]+self.nums[i]
```

The strategy is simple. We use a new list **numsSum** to store the accumulated numbers based on the given **nums** list. Then numsSum[j] - numsSum[i] + nums[i] is the range sum form i to j inclusive.