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

O(n) space O(1) query time

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public class NumArray {
    private int[] sums;

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

    public int sumRange(int i, int j) {
        if (i > j)
            return 0;
        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);