区域和检索 - 数组不可变

解法一：累加

package com.kaesar.leetcode;

public class LeetCode_303 {
    public static void main(String[] args) {
        // 测试用例
        NumArray numArray = new NumArray(new int[]{-2, 0, 3, -5, 2, -1});
        System.out.println(numArray.sumRange(0, 2)); // return 1 ((-2) + 0 + 3)
        System.out.println(numArray.sumRange(2, 5)); // return -1 (3 + (-5) + 2 + (-1))
        System.out.println(numArray.sumRange(0, 5)); // return -3 ((-2) + 0 + 3 + (-5) + 2 + (-1))
    }
}

class NumArray {

    private int[] nums;

    public NumArray(int[] nums) {
        this.nums = nums;
    }

    public int sumRange(int left, int right) {
        int result = 0;
        for (int i = left; i <= right; i++) {
            result += nums[i];
        }
        return result;
    }