class Solution { public: int Sum_Solution(int n) { int sum=n; bool ans=(n>0)&&(sum+=Sum_Solution(n-1)); return sum; } };
sum=n+(n-1)+(n-2)+...+1
class Solution { public: int Sum_Solution(int n) { int sum=n; bool ans=(n>0)&&(sum+=Sum_Solution(n-1)); return sum; } };