303. Range Sum Query

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.

本题比较简单，代码如下：

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

/**
 * Your NumArray object will be instantiated and called as such:
 * NumArray obj = new NumArray(nums);
 * int param_1 = obj.sumRange(i,j);
 */