4.6: Merging Decks

The next helper method we need is merge, which takes two sorted subdecks and returns a new deck containing all cards from both decks, in order. Here’s what the algorithm looks like in pseudocode, assuming the subdecks are named d1 and d2:

public static Deck merge(Deck d1, Deck d2) {
    // create a new deck big enough for all the cards

    // use the index i to keep track of where we are at in
    // the first deck, and the index j for the second deck
    int i = 0;
    int j = 0;
    // the index k traverses the result deck
    for (int k = 0; k < result.cards.length; k++) {

        // if d1 is empty, d2 wins
        // if d2 is empty, d1 wins
        // otherwise, compare the two cards

        // add the winner to the new deck at position k
        // increment either i or j
    }
    // return the new deck
}

One of the exercises at the end of the chapter asks you to implement merge.