算法入门-排序-插入排序

spring-boot-dependencies/spring-common/pom.xml

@@ -18,6 +18,12 @@
     </properties>
 
     <dependencies>
+        <!-- https://mvnrepository.com/artifact/edu.princeton.cs/algs4 -->
+        <dependency>
+            <groupId>edu.princeton.cs</groupId>
+            <artifactId>algs4</artifactId>
+            <version>1.0.3</version>
+        </dependency>
         <dependency>
             <groupId>org.projectlombok</groupId>
             <artifactId>lombok</artifactId>

spring-boot-dependencies/spring-common/src/main/java/io/spring/common/algorithm/sort/InsertSort.java

@@ -0,0 +1,23 @@
+package io.spring.common.algorithm.sort;
+
+/**
+ * @author xiaokexiang
+ * @since 2021/11/12
+ * 插入排序:元素依次与左边的元素进行比较，如果大于就进行交换
+ * 时间复杂度: 1 + 2 + ... + (N - 1)次比较 与 1 + 2 + ... + (N - 1)次交换 -> N^2
+ */
+public class InsertSort implements SortExample<Integer> {
+
+    @Override
+    public void sort(Integer[] ts, boolean show) {
+        for (int i = 1; i < ts.length; i++) {
+            // 依次和左边的元素进行比较，再换位
+            for (int j = i; j > 0 && less(ts[j], ts[j - 1]); j--) {
+                exchange(ts, j, j - 1);
+            }
+        }
+        if (show) {
+            show(ts);
+        }
+    }
+}

spring-boot-dependencies/spring-common/src/main/java/io/spring/common/algorithm/sort/SelectSort.java

@@ -10,8 +10,7 @@
 public class SelectSort implements SortExample<Integer> {
 
     @Override
-    public void sort(Integer[] ts) {
-
+    public void sort(Integer[] ts, boolean show) {
         for (int i = 0; i < ts.length; i++) {
             int min = i;
             // 找出最小的元素
@@ -22,12 +21,8 @@ public void sort(Integer[] ts) {
             }
             exchange(ts, i, min);
         }
-        show(ts);
-    }
-
-    public static void main(String[] args) {
-        Integer[] arrays = new Integer[]{3, 1, 2, 5, 7};
-        SelectSort selectSort = new SelectSort();
-        selectSort.sort(arrays);
+        if (show) {
+            show(ts);
+        }
     }
 }

spring-boot-dependencies/spring-common/src/main/java/io/spring/common/algorithm/sort/SortCompare.java

@@ -0,0 +1,49 @@
+package io.spring.common.algorithm.sort;
+
+import edu.princeton.cs.algs4.StdOut;
+import edu.princeton.cs.algs4.StdRandom;
+import edu.princeton.cs.algs4.Stopwatch;
+import org.springframework.util.StopWatch;
+
+import java.util.Random;
+
+/**
+ * @author xiaokexiang
+ * @since 2021/11/15
+ */
+public class SortCompare {
+
+    public static double time(String func, Integer[] a) {
+        Stopwatch stopwatch = new Stopwatch();
+        if (func.equals("Insertion")) {
+            new InsertSort().sort(a, false);
+        } else if (func.equals("Selection")) {
+            new SelectSort().sort(a, false);
+        }
+        return stopwatch.elapsedTime();
+    }
+
+
+    public static double timeRandomInput(String alg, int N, int T) {
+        double total = 0.0;
+        Integer[] a = new Integer[N];
+        for (int i = 0; i < T; i++) {
+            for (int j = 0; j < N; j++) {
+                a[j] = StdRandom.uniform(100);
+            }
+            total += time(alg, a);
+        }
+        return total;
+    }
+
+    public static void main(String[] args) {
+        String alg1 = "Insertion";
+        String alg2 = "Selection";
+        int t = 100;
+        int n = 1000;
+        double t1 = timeRandomInput(alg1, n, t);
+        double t2 = timeRandomInput(alg2, n, t);
+        StdOut.printf("For %d random Double \n %s is ", n, alg1);
+        StdOut.printf("%.1f times faster than %s\n", t2 / t1, alg2);
+    }
+}

spring-boot-dependencies/spring-common/src/main/java/io/spring/common/algorithm/sort/SortExample.java

@@ -11,7 +11,7 @@
  */
 public interface SortExample<T extends Comparable<T>> {
 
-    void sort(T[] ts);
+    void sort(T[] ts, boolean show);
 
     /**
      * 元素比较

spring-boot-dependencies/spring-common/src/main/java/io/spring/common/algorithm/sort/SortMain.java

@@ -0,0 +1,18 @@
+package io.spring.common.algorithm.sort;
+
+/**
+ * @author xiaokexiang
+ * @since 2021/11/12
+ */
+public class SortMain {
+
+    public static void main(String[] args) {
+        Integer[] arrays = new Integer[]{3, 1, 2, 5, 7};
+
+        SelectSort selectSort = new SelectSort();
+        selectSort.sort(arrays, true);
+        System.out.println();
+        InsertSort insertSort = new InsertSort();
+        insertSort.sort(arrays, true);
+    }
+}