Implement permutation of a string of length N with K letters chosen at a time (N > K). Eg: Permutation of "abc" with 2 letters chosen at a time are - ab, ac, ba, bc, ca, cb
/*
* StringPermutationsWithSize.cpp
*
* Created on: Apr 18, 2012
* Author: kiran
*/
#include <iostream>
#include <string>
#include <vector>
#include <string.h>
using namespace std;
void doPermute(string prefix, string rest, int k, vector<string> &output) {
if (k == 0) {
output.push_back(prefix);
}
else {
int len = rest.size();
for (int i=0; i<len; i++)
doPermute(prefix + rest[i], rest.substr(0, i) +
rest.substr(i+1, len - (i+1)), k - 1, output);
}
}
void permute(string input, int k, vector<string> &output) {
doPermute(string(""), input, k, output);
}
/**
* Test the code
*/
int main() {
string inp("abc");
vector<string> perms;
permute(inp, 2, perms); //choose 2 at at time
cout << "Permutations: " << perms.size() << endl;
for (unsigned int i=0; i<perms.size(); i++) {
cout << perms[i] << endl;
}
}