# [303. Range Sum Query - Immutable](https://leetcode.com/problems/range-sum-query-immutable/description/) # 思路 用一个数组sums记录和,sums[i]代表nums[0]到nums[i]的和,那么sumRange(i, j)就应该等于sum[i] - sum[i-1], 注意单独判断i得0时。 注意这种面向对象的代码风格。 # C++ ``` class NumArray { private: vector sums; public: NumArray(vector nums) { int tmp = 0; for(int num: nums) { tmp += num; sums.push_back(tmp); } } int sumRange(int i, int j) { if(i == 0) return sums[j]; else return sums[j] - sums[i - 1]; } }; ```