DSA problem
Range Sum Query - Immutable
Given an integer array nums, handle multiple queries of the following type:
- Calculate the sum of the elements of
numsbetween indicesleftandrightinclusive whereleft <= right.
Implement the NumArray class:
NumArray(int[] nums)initializes the object with the integer arraynums.int sumRange(int left, int right)returns the sum of the elements ofnumsbetween indicesleftandrightinclusive (i.e.nums[left] + nums[left + 1] + ... + nums[right]).
Because the array never changes, you can precompute a prefix-sum table once in the constructor and then answer every range query in constant time.
Examples
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) returns (-2) + 0 + 3 = 1; numArray.sumRange(2, 5) returns 3 + (-5) + 2 + (-1) = -1; numArray.sumRange(0, 5) returns (-2) + 0 + 3 + (-5) + 2 + (-1) = -3.
Constraints
- 1 <= nums.length <= 10^4
- -10^5 <= nums[i] <= 10^5
- 0 <= left <= right < nums.length
- At most 10^4 calls will be made to sumRange.
3 hints and a full solution walkthrough with step-by-step visualizations are available in the practice editor.