leetcodeRange Sum Query - Immutable

//先走一遍C++吧，最近一直写Python，老忘记打分号

class NumArray {    vector<int> mynums;public:    NumArray(vector<int> &nums) {        vector<int> tmp=nums;        if(tmp.size()>=1) mynums.push_back(tmp[0]);        for(int i = 1;i < tmp.size();i++)        {            mynums.push_back(mynums[i-1]+tmp[i]);        }            }    int sumRange(int i, int j) {        if(i == 0) return mynums[j];        else return mynums[j]-mynums[i-1];            }};// Your NumArray object will be instantiated and called as such:// NumArray numArray(nums);// numArray.sumRange(0, 1);// numArray.sumRange(1, 2);

这是我写的，速度一般般吧

看到有个大神写的，超级简练

class NumArray {private:    vector<int> acc;    public:    NumArray(vector<int> &nums) {        acc.push_back(0);        for (auto n : nums) {            acc.push_back(acc.back() + n);        }    }    int sumRange(int i, int j) {        return acc[j + 1] - acc[i];    }};// Your NumArray object will be instantiated and called as such:// NumArray numArray(nums);// numArray.sumRange(0, 1);// numArray.sumRange(1, 2);

很简练，不得不服。