README.md

307. Range Sum Query - Mutable

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

1. Update the value of an element in nums.
2. 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.
• void update(int index, int val) Updates the value of nums[index] to be val.
• 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", "update", "sumRange"]
[[[1, 3, 5]], [0, 2], [1, 2], [0, 2]]
Output:
[null, 9, null, 8]
Explanation:
NumArray numArray = new NumArray([1, 3, 5]);
numArray.sumRange(0, 2); // return 1 + 3 + 5 = 9
numArray.update(1, 2);   // nums = [1, 2, 5]
numArray.sumRange(0, 2); // return 1 + 2 + 5 = 8

Constraints:

• 1 <= nums.length <= 3 * 104
• -100 <= nums[i] <= 100
• 0 <= index < nums.length
• -100 <= val <= 100
• 0 <= left <= right < nums.length
• At most 3 * 104 calls will be made to update and sumRange.

Solutions (Python)

1. Solution

class NumArray:

    def __init__(self, nums: List[int]):
        self.tree = [0] * (len(nums) + 1)

        for i, x in enumerate(nums):
            self.update(i, x)

    def update(self, index: int, val: int) -> None:
        val -= self.sumRange(index, index)
        index += 1

        while index < len(self.tree):
            self.tree[index] += val
            index += index & -index

    def sumRange(self, left: int, right: int) -> int:
        right += 1
        ret = 0

        while right > 0:
            ret += self.tree[right]
            right -= right & -right
        while left > 0:
            ret -= self.tree[left]
            left -= left & -left

        return ret


# Your NumArray object will be instantiated and called as such:
# obj = NumArray(nums)
# obj.update(index,val)
# param_2 = obj.sumRange(left,right)