# Challenges - Permutation Challenge Solution

String Permutation Challenge Solution

The trick to string permutations is to find all permutations that begin with one letter, then all permutations that begin with a second letter, and so forth. This might suggest a recursive solution: in order to find all permutations that begin with a given letter, call permute on the remainder of the string, thereby finding all permutations of the substring using the same algorithm.

One way of coding this is as follows:

```#include <iostream>
#include <string>

using namespace std;

string swtch(string topermute, int x, int y)
{
string newstring = topermute;
newstring[x] = newstring[y];
newstring[y] = topermute[x]; //avoids temp variable
return newstring;
}
void permute(string topermute, int place)
{
if(place == topermute.length() - 1)
{
cout<<topermute<<endl;
}
for(int nextchar = place; nextchar <
topermute.length(); nextchar++)
{
permute(swtch(topermute, place, nextchar),
place+1);
}
}

int main(int argc, char* argv[])
{
if(argc!=2)
{
cout<<"Proper input is 'permute string'";
return 1;
}
permute(argv[1], 0);
}```