Question

How can I make this into a recursive function (C++)??

//Write a function that, given positive integers 1 <= n <= 10^4 and 1 <= s <= n as input, returns the sum of the last s elements in the sequence from 1 to n (inclusive).

unsigned long int suffix_sum(unsigned int n, unsigned int s){
unsigned long int sum = 0,r=(n-s)+1;
while (r<=n){
sum = sum + r;
r++;
}
return sum;
return 0;
}

Answer 1

unsigned long int suffix_sum(unsigned int n, unsigned int s){
    if(s == 0){
        return 0;
    }
    else{
        return n + suffix_sum(n-1, s-1);
    }
}