Range Sum Query - Immutable

Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive.

Example:

Given nums = [-2, 0, 3, -5, 2, -1]

sumRange(0, 2) -> 1
sumRange(2, 5) -> -1
sumRange(0, 5) -> -3

Note:

1. You may assume that the array does not change.
2. There are many calls to sumRange function.

public class NumArray {
   
    int[] sums;

    public NumArray(int[] nums) {
        this.sums = new int[nums.length + 1];
        sums[0] = 0;
        for (int i = 0; i < nums.length; i++) {
            sums[i + 1] = nums[i] + sums[i];    
        }
    }

    public int sumRange(int i, int j) {
        return sums[j + 1] - sums[i];
    }
}


// Your NumArray object will be instantiated and called as such:
// NumArray numArray = new NumArray(nums);
// numArray.sumRange(0, 1);
// numArray.sumRange(1, 2);