My c++ code:

```
class NumArray {
public:
vector<int> sum;
vector<int> a;
NumArray(vector<int> &nums) {
a.clear();
for(int i=0;i<nums.size();i++){
a.push_back(nums[i]);
}
int temp = 0;
for(int i=0;i<a.size();i++){
temp += a[i];
sum.push_back(temp);
}
}
int sumRange(int i, int j) {
if(i==0){
return sum[j];
}else{
return (sum[j]-sum[i-1]);
}
}
};
```

// Your NumArray object will be instantiated and called as such:

// NumArray numArray(nums);

// numArray.sumRange(0, 1);

// numArray.sumRange(1, 2);