https://leetcode.com/problems/running-sum-of-1d-array/description/

class Solution {
public int[] runningSum(int[] nums) {
int[] runningSum = new int[nums.length];
runningSum[0] = nums[0];
for(int i = 1; i < nums.length; i++) {
runningSum[i] = runningSum[i-1] + nums[i];
}
return runningSum;
}
}