# For loop help

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Hey,I couldn't think of a better title for this thread but here is my problem. I should write nested for loops,but I dont know the count of the loops. for example you need to list all strings can be created using the letters A B and C. But user will give you the length of the string at runtime.So you can't just write nested for next loops.
for(x = 0;x<3;x++)
{
mystring &= charlist[x];
for(y = 0;y<3;y++)
{
mystring &= charlist[y];
giveresult(mystring);
mystring = "";
}

}

// for example thats the solution for the input "2"(as length).But I need to   // "automate" it ^^


Hope I could explain my problem. have a nice day.

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Going to give you a little psudo code.

string input_str;
input_str = getString();
strLength = GetLength(input_str);

for(x = 0; x < strLength; x++)

You should be able to figure it out from here.

theTroll

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Recursion seems to be an elegant approach. You need a global string, let's call it bar. It is initially the empty string. Then you can define a method foo(int length) like this:
foo(0): write bar and a "newline" to the consolefoo(n > 0):    append 'A' to bar    foo(n - 1)    remove last character from bar    append 'B' to bar    foo(n - 1)    remove last character from bar    append 'C' to bar    foo(n - 1)    remove last character from bar

And that's basically it.

You can also do an iterative version. Just interpret a string as a number and do the increasing yourself.

Remember when you add 1 to a number, you just have to change the rightmost digit from 0 to 1, from 1 to 2, from 2 to 3... from 8 to 9. If it was already 9, you set it back to 0 and continue at the left neighbour.

Just do the same with the digits 'A', 'B' and 'C'. Here is some scaffold to get you started:

#include <string>#include <iostream>bool increase(std::string &s){    // increase the rightmost character    // if this yields a 'D', wrap around to 'A'    // and continue with next character    // (if there aren't any more, return false),    // otherwise return true}int main(){    int n = 1;    std::cin >> n;    std::string a(n, 'A');    do    {        std::cout << a << std::endl;    } while (increase(a));    return 0;}

[Edited by - DevFred on June 23, 2008 6:56:01 PM]

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Recursion works.

all(list,0) : print list, newlineall(list, n) :   all([A | list], n-1)  all([B | list], n-1)  all([C | list], n-1)print_all(n) : all([], n)

DevFred: as a general tip, never combine mutable structures and recursion. It makes things overly complicated. Think in terms of immutable structures (such as lists) instead.

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Quote:
 Original post by ToohrVykDevFred: as a general tip, never combine mutable structures and recursion.

You're totally right, but I'm still fighting with C++ to have it append something to my string with nice, clean syntax :)

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Quote:
 Original post by DevFredYou can also do an iterative version. Just interpret a string as a number and do the increasing yourself.

Can I win an obfuscated C++ contest for my perverted loop? :)
#include <iostream>#include <string>const char START = 'A';const char BOUND = 'D';bool increase(std::string &s){    for (size_t i = s.size(); i--; s = START)        if (++s != BOUND) return true;    return false;}int main(){    int n = 1;    std::cin >> n;    std::string s(n, START);    do std::cout << s << std::endl; while (increase(s));}

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Quote:
 Original post by Eralpfor example you need to list all strings can be created using the letters A B and C. But user will give you the length of the string at runtime.

Can you post a compilable example of what you have so far?

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Quote:
Original post by K-
Quote:
 Original post by Eralpfor example you need to list all strings can be created using the letters A B and C. But user will give you the length of the string at runtime.

Can you post a compilable example of what you have so far?

I was thinking of doing what troll suggested.
for(int x = 0;x<inputlength;x++){for(int d = 0;d<3;d++){mystring &= mycharlist[d];}}

but that won't do it because I want them nested. I think I'm gonna try the "iterative" version DevFred suggested.

Oh I realized you wanted full source code, here it is but it wont help because this is just a part of the whole problem that I should solve.I am not even sure that it will compile lol.

/*ID: eralp_b1PROG: namenumLANG: C++*/#include <iostream>#include <fstream>#include <string>#include <vector>#include <sstream>using namespace std;char arr[8][3] =	{		{ 'A', 'B', 'C' },		{ 'D', 'E', 'F' },		{ 'G', 'H', 'I' },		{ 'J', 'K', 'L' },		{ 'M', 'N', 'O' },		{ 'P', 'R', 'S' },		{ 'T', 'U', 'V' },		{ 'W', 'X', 'Y' }	};int main() {    ofstream fout ("namenum.out");    ifstream fin ("namenum.in");	ifstream fin2 ("dict.txt");    string bufferz;	vector<string> dict;    vector<string> results;    int* iName;	while(getline(fin2,bufferz))	{		dict.push_back(bufferz);	}	getline(fin,bufferz);    iName = new int[bufferz.length()];	for(int x = 0;x<bufferz.length();x++)		iName[x] = bufferz[x]-48;    /////////////////////////////////////////	for(int k = 0;k<bufferz.length();k++)	{		for(int m = 0;m<3;m++)		{		}	}  /////////////////////////////////////////    fout << "test" << endl;    return 0;}

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Quote:
 Original post by EralpI am not even sure that it will compile lol.

There's an easy way to find out: let the compiler try.

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