更新

Programming Pearls/第一章 开篇/BitSetTest.java

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+package cn.edu.heuet.I.basic;
+
+import java.util.ArrayList;
+import java.util.BitSet;
+import java.util.List;
+import java.util.Random;
+
+public class BitSetTest {
+	public static void main(String[] args) {
+		// 准备一百万个范围在[0-1百万)的随机数
+		final int ONE_MILLION = 100 * 10000;
+		Random random = new Random();
+		List<Integer> list = new ArrayList<>();
+		for (int i = 0; i < ONE_MILLION; i++) {
+			int randomResult = random.nextInt(ONE_MILLION);
+			list.add(randomResult);
+		}
+		// 进行位图排序
+		BitSet bitSet = new BitSet(ONE_MILLION);
+		for (int i = 0; i < ONE_MILLION; i++) {
+			// 将索引对应位设为true
+			bitSet.set(list.get(i));
+		}
+		// 测试
+		int[] test = new int[] {123,456,789,1023,4056,7089};
+		for(int i=0; i<test.length; i++) {
+			if(!bitSet.get(test[i])) {
+				System.out.println(test[i]+"已随机生成");
+			} else {
+				System.out.println(test[i]+"未生成");
+			}
+		}
+
+
+	}
+
+}

Programming Pearls/第一章 开篇/MergeSort.java

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+package cn.edu.heuet.I.basic;
+
+/**
+  * 归并排序Java语言 对<a href= "https://blog.csdn.net/morewindows/article/details/6678165">《白话经典算法系列之五归并排序的实现》</a> 
+ * C 代码的改编版
+ * @author 刘同学
+ *
+ */
+public class MergeSort {
+	// 因为要在main方法中进行测试，
+	// 所以merge()、recursion()和mergeSort()方法都加了static
+
+	// merge()方法作用:
+	// 合并两个<b>有序</b>的数列
+	// 归并排序是在“并”的时候进行排序的
+	private static void merge(int[] a, int left, int mid, int right, int[] temp) {
+		int i = left;
+		int m = mid;
+		int j = mid + 1;
+		int n = right;
+		int k = 0;
+
+		while (i <= m && j <= n) {
+			// 依次找最小，将其放入temp数组
+			if (a[i] <= a[j]) {
+				temp[k++] = a[i++];
+			} else {
+				temp[k++] = a[j++];
+			}
+		}
+		// 如果左右不对称，比较之后还剩余
+		// 那么把剩余的依次放入temp数组
+		while (i <= m) {
+			temp[k++] = a[i++];
+		}
+
+		while (j <= n) {
+			temp[k++] = a[j++];
+		}
+		// 将temp数组中的数据拷贝回去a数组
+		for (i = 0; i < k; i++) {
+			a[left + i] = temp[i];
+		}
+
+	}
+
+	// 递归recursion，合并merge
+	private static void recursion(int[] a, int left, int right, int[] temp) {
+		if (left < right) {
+			int mid = (left + right) / 2;
+
+			recursion(a, left, mid, temp);
+			/**
+			  *  上面的递归最深层是
+			 * recursion(a, 0, 0, temp);
+			 * recursion(a, 1, 1, temp);
+			 * merge(a, 0, 0, 1, temp);
+			 * 
+			  * 将a[0]和a[1]作比较后按大小放入temp数组
+			 */
+			recursion(a, mid + 1, right, temp);
+			/**
+			  *  上面的递归最深层是
+			 * recursion(a, mid+1, mid+1, temp);
+			 * recursion(a, mid+2, mid+2, temp);
+			 * merge(a, mid+1, mid+1, mid+2, temp);
+			 * 
+			  * 将a[mid+1]和a[mid+2]作比较后按大小放入temp数组
+			 */
+			merge(a, left, mid, right, temp);
+		}
+	}
+
+	public static boolean mergeSort(int[] a, int length) {
+		int[] temp = new int[length];
+		if (temp == null)
+			return false;
+		// 因为left传入0，所以right需要传入length-1
+		// 又因为merge()方法需要temp数组，所以需要加上temp
+		recursion(a, 0, length - 1, temp);
+		return true;
+	}
+
+	// 测试
+	public static void main(String[] args) {
+		int[] a = new int[] { 4, 3, 6, 1, 2, 5 };
+		mergeSort(a, a.length);
+		for (int i = 0; i < a.length; ++i) {
+			System.out.print(a[i] + " ");
+		}
+	}
+}

Programming Pearls/第一章 开篇/QuickSort.java

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+package cn.edu.heuet.I.basic;
+
+public class QuickSort {
+
+	public static void qSort(int[] arr, int left, int right) {
+		if (left >= right || arr == null || arr.length <= 1) {
+			return;
+		}
+		int i = left, j = right, mid = arr[(left + right) / 2];
+		while (i <= j) {
+			while (arr[i] < mid) {
+				++i;
+			}
+			while (arr[j] > mid) {
+				--j;
+			}
+			if (i < j) {
+				int t = arr[i];
+				arr[i] = arr[j];
+				arr[j] = t;
+				++i;
+				--j;
+			} else if (i == j) {
+				++i;
+			}
+		}
+		qSort(arr, left, j);
+		qSort(arr, i, right);
+	}
+	// 测试
+	public static void main(String[] args) {
+		int[] arr = new int[] { 1, 4, 8, 2, 3, 3 };
+		qSort(arr, 0, arr.length - 1);
+		String out = "";
+		for (int digit : arr) {
+			out += (digit + ",");
+		}
+		System.out.println(out);
+	}
+}