package crypt;

public class Permutation {
    int[] shuffled;   // shuffled sequence

    // The constructor of class Permutation creates a shuffled
    // sequence of the integers 0 ... (size-1).
    public Permutation(int size, F5Random random) {
        int i, randomIndex, tmp;
        shuffled = new int[size];

	// To create the shuffled sequence, we initialise an array
	// with the integers 0 ... (size-1).
        for (i=0; i<size; i++)	// initialise with size integers
            shuffled[i] = i;
        int maxRandom = size;	// set number of entries to shuffle
	for (i=0; i<size; i++) {	// shuffle entries
	    randomIndex = random.getNextValue(maxRandom--);
	    tmp = shuffled[randomIndex];
	    shuffled[randomIndex] = shuffled[maxRandom];
	    shuffled[maxRandom] = tmp;
	}
    }

    // get value #i from the shuffled sequence
    public int getShuffled(int i) {
	return shuffled[i];
    }
}