c++ permutations high numbers (convert code) - c++

Question

I am trying to convert this code that works for '0' - '3' strings to integer so that it will work for higher numbers
#include <string>
#include <iostream>
using namespace std;
void permutate(char[], int );
bool recurse(char[], int );
int main()
{
int strLength;
cout << "Enter your desired length: ";
cin >> strLength;
char strArray[strLength];
for (int i = 0; i<strLength; i++)
strArray[i] = '0';
permutate(strArray, sizeof(strArray));
return 0;
}
void permutate(char charArray[], int length)
{
string wait;
length--;
bool done = false;
while(!done)
{
for (int i = 0; i <= length; i++)
cout << charArray[i];
cout << endl;
if (charArray[length] == '3')
done = recurse(charArray, length);
else
charArray[length] = (char)(charArray[length]+1);
}
}
bool recurse(char charArray[], int length)
{
bool done = false;
int temp = length;
if (temp > 1)
{
charArray[temp] = '0';
if (charArray[temp-1] == '3')
{
temp--;
done = recurse(charArray, temp);
}
else
(charArray[temp-1] = (char)(charArray[temp-1] + 1));
}
else
{
charArray[temp] = '0';
if (charArray[temp-1] == '3')
done = true;
else
charArray[temp-1] = (char)(charArray[temp-1]+1);
}
return done;
}
I changed every char to int,
every '0' = 0, '3' = 3
every (charArray[temp-1] = (char)(charArray[temp-1] + 1)); to charArray[temp-1]++;
I tried to debug but I still can`t make it work :(
Manged to fix it( works for high numbers):
#include <string>
#include <iostream>
using namespace std;
void permutate(int[], int, int );
bool recurse(int[], int, int );
int main()
{
int strLength, nrElem;
cout << "Enter your desired length: ";
cin >> strLength;
cout << "Enter nr elem: ";
cin >> nrElem;
int strArray[strLength];
for (int i = 0; i<strLength; i++)
strArray[i] = 0;
permutate(strArray, strLength, nrElem );
cout << "\nSTOP";
return 0;
}
void permutate(int charArray[], int length, int nrElem)
{
// length--;
bool done = false;
while(!done)
{
for (int i = 0; i < length; i++)
cout << charArray[i] << " ";
cout << endl;
if (charArray[length - 1] == nrElem)
//done = true;
done = recurse(charArray, length, nrElem);
else
charArray[length - 1]++;
}
}
bool recurse(int charArray[], int length, int nrElem)
{
bool done = false;
int temp = length ;
if (temp > 1)
{
charArray[temp] = 0;
if (charArray[temp-1] == nrElem)
{
temp--;
done = recurse(charArray, temp, nrElem);
}
else
charArray[temp-1]++;
}
else
{
charArray[temp] = 0;
if (charArray[temp-1] == nrElem)
done = true;
else
charArray[temp-1]++;
}
return done;
}

Answer 1

In your permutate function, you're incrementing charArray[length] but checking to see if charArray[length - 1] is equal to nrElem, so you never end up calling recurse.

Answer 2

Here is a short piece of code to do the same (not an answer, however it did not look right in a comment field), not sure if you need the recursion, if you do not this code may be of interest:
#include <iostream>
#include <sstream>
using namespace std;
string output(int firstIntSize, int secondIntSize)
{
std::ostringstream oss;
for (int i = 0; i<firstIntSize; i++)
{
for (int j = 0; j< secondIntSize; j++)
{
oss << i << j << " ";
}
}
return oss.str();
}
int main()
{
cout << output(2,3);
return 0;
}

Answer 3

hmmm... Why not simply make a Permutations algorithm and then use a generic function to print whatever you are permutating. Here's how I would do it for strings:
#include <iostream>
#include <string>
template<class T>
void print(T * A, unsigned n){ //for printing purposes
for(unsigned i=0;i<n;i++){
std::cout<<A[i]<<" ";
}
std::cout<<std::endl;
}
void generate_permutations(unsigned k, std::string str, char *A, bool *U){
// k is the position that we need to fill, starts from 0 and goes to the end.
if(k<str.size()) //if k==str.size() then we will print it
for(unsigned i=0;i<str.size();i++){
if(U[i]==0){
A[k]=str[i]; U[i]=1;
generate_permutations(k+1, str, A,U);
U[i]=0; //after the recursion is finished and printed, we can release the letter.
}
}
else
print(A,str.size());
}
int main(){
std::string str;
std::cout<<"Enter the string to be permutated: \n";
std::cin>>str;
int n;
n = str.length(); // You don't really need to ask the user the size of the string he/she wants to enter.
bool *U; // we will keep track of the used letters with the help of this boolean vector
char *A; // we will copy the contents of str here, so that we keep the str intact
U = new bool[n];
for (int i=0;i<n;i++) U[i]=false;
A = new char[n];
for (int i=0;i<n;i++) A[i]=str[i];
generate_permutations(0,str,A,U);
return 0;
}
Now if you want to convert to numbers (ints), it's almost the same:
#include <iostream>
template<class T>
void print(T * A, int n){
for(int i=0;i<n;i++){
std::cout<<A[i]<<" ";
}
std::cout<<std::endl;
}
void generate_permutations(int k, int *A, bool *U, int n){
if(k==n)
print(A,n);
else {
for(int i=0;i<n;i++){
if(U[i]==0){
A[k]=i; U[i]=1;
generate_permutations(k+1,A,U,n);
U[i]=0;
}
}
}
}
int main(){
int n;
std::cout<<"Permutations of how many objects? \n";
std::cin>>n;
int * A;
bool *U;
A = new int[n];
U = new bool[n];
for (int i=0;i<n;i++) U[i]=false;
print(U, n);
generate_permutations(0,A,U,n);
return 0;
}