```
class NumArray(object):
def __init__(self, nums):
"""
initialize your data structure here.
:type nums: List[int]
"""
length = len(nums)
self.dic = {}
self.dic[(0,-1)]=0 ## sumRange(i,j), in case i==0
for j in range(length):
if j != 0:
self.dic[(0,j)] = self.dic[(0,j-1)] + nums[j]
else:
self.dic[(0,j)] = nums[j]
def sumRange(self, i, j):
"""
sum of elements nums[i..j], inclusive.
:type i: int
:type j: int
:rtype: int
"""
return self.dic[(0,j)]-self.dic[(0,i-1)]
```