leetcode-303.cpp

class NumArray {
public:
    NumArray(vector<int> nums) :psum(nums.size()+1,0){
        partial_sum(nums.begin(),nums.end(),psum.begin()+1);
    }

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

/**
 * Your NumArray object will be instantiated and called as such:
 * NumArray obj = new NumArray(nums);
 * int param_1 = obj.sumRange(i,j);
 */