LeetCode – 303. 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.

When I saw this question, I was completely stumped. It wasn't just about writing an algorithm; it was about writing a small program.

public class NumArray { public int[] sums; public NumArray(int[] nums) { if(nums.length == 0) return; sums = new int[nums.length]; sums[0] = nums[0]; for(int i=1;i