303. Range Sum Query - Immutable.py

"""
Given an integer array nums, handle multiple queries of the following type:

Calculate the sum of the elements of nums between indices left and right inclusive where left <= right.
Implement the NumArray class:

NumArray(int[] nums) Initializes the object with the integer array nums.
int sumRange(int left, int right) Returns the sum of the elements of nums between indices left and right inclusive
(i.e. nums[left] + nums[left + 1] + ... + nums[right]).

Example 1:

    Input
        ["NumArray", "sumRange", "sumRange", "sumRange"]
        [[[-2, 0, 3, -5, 2, -1]], [0, 2], [2, 5], [0, 5]]

    Output
        [null, 1, -1, -3]

    Explanation
        NumArray numArray = new NumArray([-2, 0, 3, -5, 2, -1]);
        numArray.sumRange(0, 2); // return (-2) + 0 + 3 = 1
        numArray.sumRange(2, 5); // return 3 + (-5) + 2 + (-1) = -1
        numArray.sumRange(0, 5); // return (-2) + 0 + 3 + (-5) + 2 + (-1) = -3

"""
from typing import List


class NumArray:

    def __init__(self, nums: List[int]):
        self._sums = nums
        for i in range(1, len(nums)):
            self._sums[i] = nums[i] + self._sums[i - 1]

    def sumRange(self, left: int, right: int) -> int:
        if left == 0:
            return self._sums[right]
        return self._sums[right] - self._sums[left - 1]

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