digit sum in c++ code example

Example 1: c++ sum of all numbers up to a number

// Method 1: Mathematical -> Sum up numbers from 1 to n 
int sum(int n){
	return (n * (n+1)) / 2;
}

// Method 2: Using a for-loop -> Sum up numbers from 1 to n 
int sum(int n){
	int tempSum = 0; 
  	for (int i = n; i > 0; i--){
     	tempSum += i;  
    }
  	return tempSum; 
}

// Method 3: Using recursion -> Sum up numbers from 1 to n 
int sum(int n){
	return n > 0 ? n + sum(n-1) : 0; 
}

Example 2: C++ sum the digits of an integer

// sum the digits of an integer
int getSum(long long n){
  int sum = 0;
  int m = n;
  while(n>0) {    
    m=n%10;    
    sum=sum+m;    
    n=n/10;    
  } 
  return sum;
}