sum of integers function 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: how to sum all numbers under a given number c++
#include <iostream>
#include <math.h>
// "#include <math.h> isn't needed.
using namespace std;
/* run this program using the console pauser or add your own getch, system("pause") or input loop */
int main(int argc, char** argv) {
// Sum of numbers in a group under a given number.
cout << "Insert four numbers:" << endl;
// In this case the numbers I chose to use are four but you can use how many you want.
float a, b, c, d;
cin >> a >> b >> c >> d;
float aa, bb, cc, dd;
// The second set of variables must have the same number of variables of the numbers
// you want to sum.
if(a < 8){
// In this case "n" is replaced by 8, but, again, you can use any number you prefer.
aa = a;
if(b < 8){
bb = b;
if(c < 8){
cc = c;
if(d < 8){
dd = d;
} else {
dd = 0;
}
} else {
cc = 0;
if(d < 8){
dd = d;
} else {
dd = 0;
}
}
} else {
bb = 0;
if(c < 8){
cc = c;
if(d < 8){
dd = d;
} else {
dd = 0;
}
} else {
cc = 0;
if(d < 8){
dd = d;
} else {
dd = 0;
}
}
}
} else {
aa = 0;
if(b < 8){
bb = b;
if(c < 8){
cc = c;
if(d < 8){
dd = d;
} else {
dd = 0;
}
} else {
cc = 0;
if(d < 8){
dd = d;
} else {
dd = 0;
}
}
} else {
bb = 0;
if(c < 8){
cc = c;
if(d < 8){
dd = d;
} else {
dd = 0;
}
} else {
cc = 0;
if(d < 8){
dd = d;
} else {
dd = 0;
}
}
}
}
cout << endl << "Sum of the numbers lower than n (8): " << aa+bb+cc+dd << endl;
// Basically this associates each number to a variable of the second group and
// then, through if, it sees which numbers are under n.
// If they are under n the second variable is given the same numeric value as
// its respective number, if not its value is equal to 0.
// It then sums the variables together.
// To have more/less numbers you add the respective variables, then make two
// cases where the number is higher or lower than n. Then, you copy-paste
// the two if chains underneath.
return 0;
}