Use recursion to do 1+2+3+...+n summation

Seek 1+2+3+…+n, it is required that keywords such as multiplication and division, for, while, if, else, switch, case and conditional judgment statements (A?B:C) cannot be used.

Analysis: The easiest way to do it with recursion. Loop call

public int Sum(int n) {
    
    
            int i = 1 % n;
            return n + Sum_Solution_2(n - 1);
        }