15算法课程 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) -> 1sumRange(2, 5) -> -1sumRange(0, 5) -> -3

Note:

1. You may assume that the array does not change.
2. There are many calls to sumRange function.

solution:

本题很简单，就考察了类的使用

code:

class NumArray {public:    NumArray(vector<int> nums) {        accu.push_back(0);        for (int num : nums)            accu.push_back(accu.back() + num);    }    int sumRange(int i, int j) {        return accu[j + 1] - accu[i];    }private:    vector<int> accu;};