Question

Give a big-O estimate for the number additions used in this segment of an algorithm.
t := 0
for i := 1 to n
for j := 1 to n
t := t + i + j
I understand the answer is O(n^2) but how?

Answer 1

i am not sure exactly what the sum is you are asking, but \(\sum_{k=1}^nk=\frac{n(n+1)}{2}\) which is certaily \(O(n^2)\) but maybe that is not the question