Google's 3-Part Winning Tile Coding Question

Google interviewers often start small on purpose: write the function signature before any logic, then build up, then change the spec on you. It tests whether your first design is clean enough to bend. Here is the full Winning Tile question, Java for each part, and the rubric.

The question

Part 1 · The signature

Resist writing logic. A precise signature, clear parameters, a documented return contract, is the artifact being graded here. Get the contract right and Parts 2 and 3 are small.

/**
 * Decide which player wins by comparing their hands of tiles.
 *
 * @param handA player A's tiles (each value 1..10)
 * @param handB player B's tiles
 * @return 1 if A wins, 2 if B wins, 0 on a tie
 */
int winner(int[] handA, int[] handB) {
    return 0; // Part 1: signature only
}

Part 2 · Compare the highest tile

Whoever holds the single highest tile wins. A linear max over each hand, then compare. O(n) time, O(1) space.

int winner(int[] handA, int[] handB) {
    int hiA = max(handA), hiB = max(handB);
    if (hiA > hiB) return 1;
    if (hiB > hiA) return 2;
    return 0;
}

private int max(int[] hand) {
    int m = Integer.MIN_VALUE;
    for (int v : hand) m = Math.max(m, v);
    return m;
}

Part 3 · The spec change

Tiles are now strings: digits 2 to 9, plus A = 1, B = 10, and C = 11. The comparison logic does not change at all; only how you read a tile's value does. Isolate that in one function and the rest of Part 2 stands.

int winner(String[] handA, String[] handB) {
    int hiA = maxValue(handA), hiB = maxValue(handB);
    return hiA > hiB ? 1 : (hiB > hiA ? 2 : 0);
}

private int maxValue(String[] hand) {
    int m = Integer.MIN_VALUE;
    for (String t : hand) m = Math.max(m, value(t));
    return m;
}

private int value(String tile) {
    switch (tile) {
        case "A": return 1;
        case "B": return 10;
        case "C": return 11;
        default:  return Integer.parseInt(tile); // "2".."9"
    }
}

If the spec change forced you to touch the comparison logic, that is the signal. A clean Part 2 localizes the change to value() alone.

How Google scores it

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