Write a function sum_to_n(n) that returns 1 + 2 + 3 + ... + n using a loop. When n is 0 there is nothing to add, so return 0.
In maths notation this is \sum_{i=1}^{n} i. To check your answer, compare it with Gauss's formula \frac{n(n+1)}{2}: for n = 4 that is \frac{4 \cdot 5}{2} = 10.
Examples
Input: n = 4
Output: 10
Explanation: 1 + 2 + 3 + 4 = 10
Input: n = 0
Output: 0
Constraints
0 <= n <= 10**5
Goals
- Use a for loop with range() to visit every number from 1 to n
- Keep a running total in a variable