初心者向けの課題(バブルソート/リニアサーチ/バイナリサーチ)

制御文しかしらない人を対象とした課題の解答。

public class BubbleSortSample {
    public static void main(String[] args) {

        int[] numbers = { 5, 3, 2, 1, 4 };

        for (int i = 0; i < numbers.length; i++) {
            int unsortedLength = numbers.length - i;

            for (int j = 0; j < unsortedLength - 1; j++) {

                if (numbers[j + 1] < numbers[j]) {
                    int temporary = numbers[j];
                    numbers[j] = numbers[j + 1];
                    numbers[j + 1] = temporary;
                }

            }
        }

        for (int i : numbers) {
            System.out.println(i);
        }

    }
}

public class LinearSearchSample {

    public static void main(String[] args) {

        int[] numbers = { 5, 4, 2, 1, 3 };
        int target = 3;

        int index = -1;
        for (int i = 0; i < numbers.length; i++) {

            if (numbers[i] == target) {
                index = i;
                break;
            }

        }

        if (index == -1) {
            System.out.println(target + "は見つかりませんでした。");
        } else {
            System.out.println(target + "は" + (index + 1) + "番目にあります。");
        }

    }
}

public class BinarySearchSample {

    public static void main(String[] args) {

        int[] numbers = { 1, 2, 3, 4, 5 };
        int target = 3;

        int index = -1;

        int startIndex = 0;
        int endIndex = numbers.length - 1;

        while (startIndex <= endIndex) {

            int centerIndex = (startIndex + endIndex) / 2;
            if (numbers[centerIndex] == target) {
                index = centerIndex;
                break;
            } else if (numbers[centerIndex] < target) {
                startIndex = centerIndex + 1;
            } else {
                endIndex = centerIndex - 1;
            }

        }

        if (index == -1) {
            System.out.println(target + "は見つかりませんでした。");
        } else {
            System.out.println(target + "は" + (index + 1) + "番目にあります。");
        }

    }
}