Factors

#include <iostream>
#include <cstdlib>
#include <math.h>
#include <vector>
#include <algorithm>

//Find factors of a number

using namespace std;

int main(int argc, char *argv[]) {
    int n;
    vector<int> vec;
    if(argc==1) {
        cout << "Enter a positive decimal number: ";
        cin >> n;
    } else n=atoi(argv[1]);
    cout << "Factors of " << n << " are:\n";
    for(int i=1;i<=sqrt(n);i++) { //Reduce time complexity of O(n) to O(sqrt(n))
         //when a*b=n then a and b both are the factors
        if(n%i==0) {
            vec.push_back(i);
            if(i!=sqrt(n)) //do not include b if a=b
                vec.push_back(n/i);
        }
    }
    sort(vec.begin(),vec.end());//sort the vector
    vector<int>::iterator v=vec.begin();
    while(v!=vec.end()) {
        cout << *v << endl;
        v++;
    }
    return 0;
}