303_range_sum_query_immutable.py

# Solution 1

class NumArray:

    def __init__(self, nums: List[int]):
        self.arr = nums[:]

    def sumRange(self, i: int, j: int) -> int:
        ans = 0
        for index in range(i, j+1):
            ans += self.arr[index]
        return ans


# Your NumArray object will be instantiated and called as such:
# obj = NumArray(nums)
# param_1 = obj.sumRange(i,j)


# Solution 2

class NumArray:

    def __init__(self, nums: List[int]):
        self.nums_sum = []
        for i in range(len(nums)):
            if i == 0:
                self.nums_sum.append(nums[i])
            else:
                self.nums_sum.append(self.nums_sum[i-1]+nums[i])

    def sumRange(self, i: int, j: int) -> int:
        if i == 0:
            return self.nums_sum[j]
        else:
            return self.nums_sum[j] - self.nums_sum[i-1]


# Your NumArray object will be instantiated and called as such:
# obj = NumArray(nums)
# param_1 = obj.sumRange(i,j)

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