Problem

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

Solution

class NumArray {    public int[] sum;    public NumArray(int[] nums) {        if (nums == null || nums.length == 0) return;        sum = new int[nums.length+1];        for (int i = 1; i <= nums.length; i++) {            sum[i] = sum[i-1]+nums[i-1];        }    }        public int sumRange(int i, int j) {        return sum[j+1]-sum[i];    }}