Range Sum Query - Immutable(区域和检索 - 数组不可变)

[https://leetcode-cn.com/problems/range-sum-query-immutable/](https://leetcode-cn.com/problems/range-sum-query-immutable/)

```
/**
*time:2019/12/11
**/

class NumArray {
//方法一
// private int[] data;
// public NumArray(int[] nums) {
// data=nums;
// }

// public int sumRange(int i, int j) {
// int sum=0;
// for(int k=i;k<=j;k++)
// {
// sum+=data[k];
// }
// return sum;
// }
//方法二
private int[] sum;
public NumArray(int[] nums)
{
sum=new int[nums.length+1];
for(int i=0;i