303. 区域和检索 - 数组不可变

题目链接：https://leetcode.cn/problems/range-sum-query-immutable/description/

Java

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

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