实现

ExponentialDiffusionBinarySearch.java

/**
 * 基于指数扩散二分查找的重名文件搜索
 * @author
 */
public class ExponentialDiffusionBinarySearch {

    public static String repeatNumber = "200";

    public static int repeatNumberSize = Integer.parseInt(repeatNumber);

    public static String originalFileName = "1232121421412(0).jpg";

    /**
     * 线性查找
     * @param originalFileName
     * @return long
     */
    public static long linearSearch(String originalFileName) {
        long start = System.currentTimeMillis();

        Boolean repeat = true;

        // 如果存在重名，则加(1)后缀
        if (repeat) {
            StringBuilder fileName = new StringBuilder();
            // 后缀数字初始化
            int suffixNumber = 0;
            String fileExtensionName = "";

            // 分离文件拓展名(.jpg .png ... )
            for (int i = originalFileName.length() - 1; i > 0; i--) {
                if (originalFileName.charAt(i) == '.') {
                    fileExtensionName = originalFileName.substring(i, originalFileName.length());
                    fileName = new StringBuilder(originalFileName.substring(0, i));
                    break;
                }
            }
            // 加_1后缀
            fileName.append("_" + ++suffixNumber);
            repeat = true;

            // 如果已经存在 _1 后缀，则改为 _2 , _3 ,...直到不重复为止
            while (repeat) {
                // 把我们添加的"_"后面所有数字字符删除
                for (int length = fileName.length(); length > 0; length--) {
                    char c = fileName.charAt(length - 1);
                    if (c != '_') {
                        fileName.delete(length - 1, length);
                    } else {
                        break;
                    }
                }
                // 在"_"后面添加++suffixNumber
                fileName.append(++suffixNumber);
                // 【重复判断】模拟O(n)的全图片集扫描
                for (int i = 0; i < repeatNumberSize; i++) {
                    // 假设_repeatNumber时不再重复
                    if (repeatNumber.equals(fileName.substring(fileName.length() - repeatNumber.length(), fileName.length()))) {
                        repeat = false;
                        break;
                    }
                }
//                System.out.println(repeat + " " + fileName);
            }
            // 合并扩展名后返回
            fileName.append(fileExtensionName);
            System.out.println(fileName);
        }
        long end = System.currentTimeMillis();
        return (end - start);
    }

    /**
     * 指数扩散二分查找
     * @param originalFileName
     * @return long
     */
    public static long exponentialDiffusionBinarySearch(String originalFileName) {
        long start = System.currentTimeMillis();

        Boolean repeat = true;

        // 如果存在重名，则加(1)后缀
        if (repeat) {
            StringBuilder fileName = new StringBuilder();
            // 后缀数字初始化
            int suffixNumber = 0;
            String fileExtensionName = "";

            // 分离文件拓展名(.jpg .png ... )
            for (int i = originalFileName.length() - 1; i > 0; i--) {
                if (originalFileName.charAt(i) == '.') {
                    fileExtensionName = originalFileName.substring(i, originalFileName.length());
                    fileName = new StringBuilder(originalFileName.substring(0, i));
                    break;
                }
            }
            // 加_1后缀
            fileName.append("_" + ++suffixNumber);
            repeat = true;

            int left = 1;
            int mid = 1;
            int right = 2;
            boolean rightFind = repeat;

            // 1.指数扩散，右边界扩散至无目标区
            while (rightFind) {
                // 左边界跟进，缩小范围
                left = mid;
                // 右边界指数扩张，继续搜索
                right = right * 2;
                // 二分法试探
                mid = (left + right) / 2;
                // 【判断重复】假设_right下标不再重复
                if (repeatNumberSize < right) {
                    rightFind = false;
                }
            }

            // 【判断重复】
            repeat = (mid < repeatNumberSize) ? true : false;
            // 2.二分查找
            while (repeat.equals(Boolean.TRUE) || left < right) {
                // 把我们添加的"_"后面所有数字字符删除
                for (int length = fileName.length(); length > 0; length--) {
                    char c = fileName.charAt(length - 1);
                    if (c != '_') {
                        fileName.delete(length - 1, length);
                    } else {
                        break;
                    }
                }

                if (repeat) {
                    // 左边界跟进，缩小范围
                    left = mid + 1;
                }
                else {
                    // 右边界收回，缩小范围
                    right = mid;
                }
                // 二分法试探
                mid = (left + right) / 2;

                // 在"_"后面添加 mid
                fileName.append(mid);
                // 模拟O(n)的全图片集扫描，【判断重复】
                for (int i = 0; i < repeatNumberSize; i++) {
                    // 假设_repeatNumber时不再重复
                    if (mid < repeatNumberSize) {
                        repeat = true;
                        break;
                    }
                    else if (repeatNumberSize <= mid) {
                        repeat = false;
                        break;
                    }
                }

//                System.out.println(repeat + " " + fileName);
            }
            // 合并扩展名后返回
            fileName.append(fileExtensionName);
            System.out.println(fileName);
        }
        long end = System.currentTimeMillis();
        return (end - start);
    }


    public static void main(String[] args) {

        long time1 = linearSearch(originalFileName);
        System.out.println("linearSearch 运行时间：" + time1 + "(ms)");

        long time2 = exponentialDiffusionBinarySearch(originalFileName);
        System.out.println("exponentialDiffusionBinarySearch 运行时间：" + time2 + "(ms)");
    }
}

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