303. Range Sum Query - Immutable

不是算法题，大概是考constructer的吧？？？

public class NumArray {
    int[] nums;
    
    public NumArray(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];
    }
}


// Your NumArray object will be instantiated and called as such:
// NumArray numArray = new NumArray(nums);
// numArray.sumRange(0, 1);
// numArray.sumRange(1, 2);