Question

Thank you all for helping. Below this post I put the corrected version’s of both scripts which now produce the equal output.

---

Hello,

I have written a little brute string generation script in python to generate all possible combinations of an alphabet within a given length. It works quite nice, but for the reason I wan’t it to be faster I try to port it to C++.

The problem is that my C++ Code is creating far too much combination for one word.
Heres my example in python:

./test.py

gives me

aaa
aab
aac
aad
aa
aba
....

while ./test (the c++ programm gives me)

aaa
aaa
aaa
aaa
aa

Here I also get all possible combinations, but I get them twice ore more often.

Here is the Code for both programms:

 #!/usr/bin/env python
 import sys
 #Brute String Generator
 #Start it with ./brutestringer.py 4 6 "abcdefghijklmnopqrstuvwxyz1234567890" ""
 #will produce all strings with length 4 to 6 and chars from a to z and numbers 0 to 9
 def rec(w, p, baseString):
    for c in "abcd":
        if (p<w - 1):
            rec(w, p + 1, baseString + "%c" % c)
         print baseString

 for b in range(3,4):
     rec(b, 0, "")

And here the C++ Code

 #include <iostream>
 using namespace std;
 string chars="abcd";

 void rec(int w,int b,string p){
    unsigned int i;
    for(i=0;i<chars.size();i++){
        if(b < (w-1)){
            rec(w, (b+1), p+chars[i]);
        }
        cout <<  p << "\n"; 
    }
 }


 int main ()
 {
    int a=3, b=0;
    rec (a+1,b, "");
    return 0;
 }

Does anybody see my fault ? I don’t have much experience with C++.

Thanks indeed

---

Here the corrected version:

C++

#include <iostream>
using namespace std;
string chars="abcd";

void rec(int w,int b,string p){
    unsigned int i;
    for(i=0;i<chars.size();i++){
        if(b < (w)){
            rec(w, (b+1), p+chars[i]);
        }
    }
    cout << p << "\n";
}


int main ()
{
    rec (3,0, "");
    return 0;
}

Python

#!/usr/bin/env python
import sys

def rec(w, b, p):
    for c in "abcd":
        if (b < w - 1):
            rec(w, b + 1, p + "%c" % c)
    print p

rec(4, 0, "")

Equal Output:

$ ./test > 1
$ ./test.py 3 3 "abcd" "" > 2
$ diff 1 2
$ 

Answer 1

I think the Python code is also broken but maybe you don’t notice because the print is indented by one space too many (hey, now I’ve seen a Python program with a one-off error!)

Shouldn’t the output only happen in the else case? And the reason why the output happens more often is that you call print/cout 4 times. I suggest to change the code:

def rec(w, p, baseString):
    if w == p:
        print baseString
    else:
        for ...