Range Sum Query - Immutable(leetcode303)

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 RangeSumQueryImmutable303 {

    int[] nums;

    public RangeSumQueryImmutable303(int[] nums) {
        for(int i = 1; i < nums.length; i++) {
            nums[i] += nums[i - 1];
        }
        this.nums = nums;
    }

    public int sumRange(int i, int j) {
        if(i == 0) {
            return nums[j];
        }
        return nums[j] - nums[i - 1];
    }
}

git:https://github.com/woshiyexinjie/leetcode-xin