Q303.cpp

class NumArray {
public:
    NumArray(vector<int> &nums) {
        if(nums.empty())
            return;
        sums.resize(nums.size()+1);
        for(int i=1; i<sums.size(); i++){
            sums[i] = sums[i-1]+nums[i-1];
        }
    }

    int sumRange(int i, int j) {
        return sums[j+1]-sums[i];
    }
    vector<int> sums;
};


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