Why does this code add an extra zero to my number? [closed] - c++

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The following code
#include "stdafx.h"
#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
bool qualities(double number){
//function qualities, irrelevant to question
}
int main(){
double pandigital = 123456789;
double sum = 0;
string strpan = to_string(pandigital);
while (next_permutation(strpan.begin(), strpan.end())){
cout << strpan << endl;
if (qualities(pandigital)){
sum += pandigital;
}
next_permutation(strpan.begin(), strpan.end());
break;
}
cout << "sum is " << sum << endl;
cin.get();
}
has the following problems beginning at this piece of code
double pandigital = 123456789;
double sum = 0;
string strpan = to_string(pandigital);
while (next_permutation(strpan.begin(), strpan.end())){
cout << strpan << endl;
The problem is strpan has an extra zero appended to it, which is an error. If I add a zero to pandigital so we have 1234567890, it will still append an extra zero.

Answer 1

Zero comes from std::to_string converting a double to string: rather than producing "123456789", it makes "123456789.0".
To fix this problem, declare pandigital as int, or add a cast when converting it to a string:
string strpan = to_string((int)pandigital);
With this issue out of the way, you have another fix to make: each iteration of your while loop calls next_permutation twice - once in the header of the loop, and once in the body. You should remove the invocation that you perform in the body of the loop.
Finally, recall that in order to go through all possible permutations the initial call of next_permutation should be made when the range is sorted. It is not a problem for your number, because the digits are arranged in ascending order, but it may become an issue if you start with a different number.