c++ - Basic Value Swap function -

i'm trying design piece of code works this. user enters 3 digit number, let's chose 653, input numbers in integer wish swap around. example:

enter number , values wish swap: "653 2 3" 

this returns following value:

635 new number.  

i trying in function called digit_swap. im not sure how approach i'm new coding , newer coding. think have seperate integer units, tens , hundred components , did following:

third = (number % 10); second = ((number % 100)/10); first = ((number % 1000)/100); 

the thing is, use bunch of if statements determine swapping of numbers or loop. have no idea how go this. code have following.

#include <iostream>  using std::cin; using std::cout; using std::endl;  int digit_swap(int number, int inputone, int inputtwo) {  int first, second, third;      if (number < 100) {         cout << "please enter 3 digit integer\n";         exit(0);     }     else if (number >= 1000) {         cout << "please enter 3 digit integer\n";         exit(0);     }     else {          third = (number % 10);         second = ((number % 100)/10);         first = ((number % 1000)/100);      }    }  using namespace std; int main() {     int option_one, option_two;     int number;     cin >> number;     cin >> option_one >> option_two;     digit_swap(number, option_one, option_two);     cout << "new number = " << number;  } 

even when test see if working adding return first in else segment of if statement returns nothing. appreciated, i'm not asking code me either.

int digit_swap(int number, int inputone, int inputtwo) {      int first, second, third;      if (number < 100) {         // doing      }     else {         third = (number % 10);         number /= 10;         second = (number % 10);         number /= 10;         first = (number % 10);         number /= 10;     }     if(inputone == 1) {         if(inputtwo == 2) {             number += second*100 + first*10 + third;         }         else if(inputtwo == 3) {             number += third*100 + second*10 + first;         }         else{;}     }     else if(inputone == 2) {         if(inputtwo == 3) {             number += first*100 + third*10 + second;         }     }     else{;}     return number; }