第三周作业——冒泡排序(BubbleSort)与归并排序(MergeSort)

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冒泡排序(BubbleSort)

基本思想：两两比较待排序数据元素的大小，发现两个数据元素的次序相反时即进行交换，直到没有反序的数据元素为止。

程序代码如下：

import java.io.BufferedReader;  import java.io.File;  import java.io.FileOutputStream;  import java.io.FileReader;  import java.io.IOException;  import java.util.ArrayList;    public class bubbleSort {        public static void main(String[] args) {                  double start_all = System.currentTimeMillis();          String path = "src/largeW.txt";          ArrayList<Integer> list = read(path);          int temp;          double start = System.currentTimeMillis();          for (int i = 0; i < list.size(); i++) {              for (int j = i; j < list.size(); j++) {                  if (list.get(i) > list.get(j)) {                      temp = list.get(i);                      list.set(i, list.get(j));                      list.set(j, temp);                  }              }          }          double end = System.currentTimeMillis();          System.out.println("冒泡排序时间为: " + (end - start)+"毫秒");          // 写入txt文件          write(list);          System.out.println("成功写入");          double end_all = System.currentTimeMillis();          System.out.println("总运行时间为: " + (end_all - start_all)+"毫秒");      }      //创建并写入largeW_bubble.txt文件      public static void write(ArrayList list) {          File f = new File("src/largeW_bubble.txt");          FileOutputStream fou = null;          try {                fou = new FileOutputStream(f, true);              for (int i = 0; i < list.size(); i++) {                  String s = list.get(i).toString();                  String a = "" + s + "\t\n";                  // byte []bytes=new byte[1024];                  // 如何把string转换byte数组                  fou.write(a.getBytes());                }          } catch (Exception e) {              // TODO: handle exception              e.printStackTrace();          } finally {              try {                  fou.close();              } catch (Exception e) {                  // TODO Auto-generated catch block                  e.printStackTrace();              }          }      }      //读取文件到Arraylist 数组      public static ArrayList read(String path) {          ArrayList<Integer> list = new ArrayList<Integer>();          BufferedReader input = null;          try {              FileReader in = new FileReader(path);              input = new BufferedReader(in);              String ss;              try {                  while ((ss = input.readLine()) != null) {                      String[] s = ss.split("\r\n");                      for (int i = 0; i < s.length; i++) {                          list.add(Integer.parseInt(s[i].trim())); // 将String s中的内容添加到动态数组中                      }                  }              } catch (IOException e) {                  // TODO 自动生成的 catch 块                  e.printStackTrace();              }              in.close();              input.close();          } catch (Exception e) {                e.printStackTrace();          }            return list;      }    }

归并排序：

  import java.io.BufferedReader;  import java.io.File;  import java.io.FileOutputStream;  import java.io.FileReader;  import java.io.IOException;  import java.util.ArrayList;    public class mergeSort {        public static void main(String[] args) {              double start_all = System.currentTimeMillis();          String path = "src/largeW.txt";          ArrayList<Integer> list=read(path);           double start = System.currentTimeMillis();          mergeSort(list);          double end = System.currentTimeMillis();          System.out.println("归并排序时间为: " + (end - start)+"毫秒");          // 写入txt文件          write(list);          System.out.println("写入完成");          double end_all = System.currentTimeMillis();          System.out.println("总运行时间为: " + (end_all - start_all)+"毫秒");      }      //创建并写入largeW_merge.txt文件      public static void write(ArrayList<Integer> list) {          File f = new File("src/txt/largeW_merge.txt");          FileOutputStream fou = null;          try {                fou = new FileOutputStream(f, true);                for (int i = 0; i < list.size(); i++) {                  String s = String.valueOf(list.get(i));                  String a = "" + s + "\t\n";                  // byte []bytes=new byte[1024];                       fou.write(a.getBytes());                }          } catch (Exception e) {              // TODO: handle exception              e.printStackTrace();          } finally {              try {                  fou.close();              } catch (Exception e) {                  // TODO Auto-generated catch block                  e.printStackTrace();              }          }      }            //归并排序      public static void mergeSort(ArrayList<Integer> data) {            sort(data, 0, data.size() - 1);        }            public static void sort(ArrayList<Integer> data, int left, int right) {            if (left >= right)                return;            // 找出中间索引            int center = (left + right) / 2;            // 对左边数组进行递归            sort(data, left, center);            // 对右边数组进行递归            sort(data, center + 1, right);            // 合并            merge(data, left, center, right);                }                public static void merge(ArrayList<Integer> data, int left, int center, int right) {            // 临时数组            int[] tmpArr = new int[data.size()];            // 右数组第一个元素索引            int mid = center + 1;            // third 记录临时数组的索引            int third = left;            // 缓存左数组第一个元素的索引            int tmp = left;            while (left <= center && mid <= right) {                // 从两个数组中取出最小的放入临时数组                if (data.get(left) <= data.get(mid)) {                    tmpArr[third++] = data.get(left++);                } else {                    tmpArr[third++] = data.get(mid++);                }            }              while (mid <= right) {                tmpArr[third++] = data.get(mid++);            }            while (left <= center) {                tmpArr[third++] = data.get(left++);            }             while (tmp <= right) {          data.set(tmp, tmpArr[tmp++]);          }        }                    //读取文件到int数组      public static ArrayList read(String path) {          ArrayList<Integer> list = new ArrayList<Integer>();          BufferedReader input = null;          try {              FileReader in = new FileReader(path);              input = new BufferedReader(in);              String ss;              try {                  while ((ss = input.readLine()) != null) {                      String[] s = ss.split("\r\n");                      for (int i = 0; i < s.length; i++) {                          list.add(Integer.parseInt(s[i].trim())); // 将String s中的内容添加到动态数组中                      }                  }              } catch (IOException e) {                               e.printStackTrace();              }              in.close();              input.close();          } catch (Exception e) {                   e.printStackTrace();          }            return list;      }    }

运行结果：

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