https://leetcode.com/problems/running-sum-of-1d-array
Source
vector<int> runningSum(vector<int>& nums) {
vector<int> viAns;
int sum = 0;
for(int i=0; i<nums.size(); ++i){
sum += nums[i];
viAns.push_back(sum);
}
return viAns;
}