插入排序【Java]

  1 package class01;
  2
  3 import java.util.Arrays;
  4
  5 public class Code03_InsertionSort {
  6
  7     public static void insertionSort(int[] arr) {
  8         if (arr == null || arr.length < 2) {
  9             return;
 10         }
 11         for (int i = 1; i < arr.length; i++) {
 12             for (int j = i - 1; j >= 0 && arr[j] > arr[j + 1]; j--) {
 13                 swap(arr, j, j + 1);
 14             }
 15         }
 16     }
 17
 18     public static void swap(int[] arr, int i, int j) {
 19         arr[i] = arr[i] ^ arr[j];
 20         arr[j] = arr[i] ^ arr[j];
 21         arr[i] = arr[i] ^ arr[j];
 22     }
 23
 24     // for test
 25     public static void comparator(int[] arr) {
 26         Arrays.sort(arr);
 27     }
 28
 29     // for test
 30     public static int[] generateRandomArray(int maxSize, int maxValue) {
 31         int[] arr = new int[(int) ((maxSize + 1) * Math.random())];        //长度随机
 32         for (int i = 0; i < arr.length; i++) {
 33             arr[i] = (int) ((maxValue + 1) * Math.random()) - (int) (maxValue * Math.random());
 34         }
 35         return arr;
 36     }
 37
 38     // for test
 39     public static int[] copyArray(int[] arr) {
 40         if (arr == null) {
 41             return null;
 42         }
 43         int[] res = new int[arr.length];
 44         for (int i = 0; i < arr.length; i++) {
 45             res[i] = arr[i];
 46         }
 47         return res;
 48     }
 49
 50     // for test
 51     public static boolean isEqual(int[] arr1, int[] arr2) {
 52         if ((arr1 == null && arr2 != null) || (arr1 != null && arr2 == null)) {
 53             return false;
 54         }
 55         if (arr1 == null && arr2 == null) {
 56             return true;
 57         }
 58         if (arr1.length != arr2.length) {
 59             return false;
 60         }
 61         for (int i = 0; i < arr1.length; i++) {
 62             if (arr1[i] != arr2[i]) {
 63                 return false;
 64             }
 65         }
 66         return true;
 67     }
 68
 69     // for test
 70     public static void printArray(int[] arr) {
 71         if (arr == null) {
 72             return;
 73         }
 74         for (int i = 0; i < arr.length; i++) {
 75             System.out.print(arr[i] + " ");
 76         }
 77         System.out.println();
 78     }
 79
 80     // for test
 81     public static void main(String[] args) {
 82         int testTime = 500000;
 83         int maxSize = 100;
 84         int maxValue = 100;
 85         boolean succeed = true;
 86         for (int i = 0; i < testTime; i++) {
 87             int[] arr1 = generateRandomArray(maxSize, maxValue);
 88             int[] arr2 = copyArray(arr1);
 89             insertionSort(arr1);
 90             comparator(arr2);
 91             if (!isEqual(arr1, arr2)) {
 92                 succeed = false;
 93                 break;
 94             }
 95         }
 96         System.out.println(succeed ? "Nice!" : "Fucking fucked!");
 97
 98         int[] arr = generateRandomArray(maxSize, maxValue);
 99         printArray(arr);
100         insertionSort(arr);
101         printArray(arr);
102     }
103
104 }

插入排序的本质：假如有5个数【3,2,4,1,6】第一次选择第1个和第2个数，也就是i=1;j=i-1（j=0）然后比较大小（arr[j] > arr[j + 1]; 前一个数和后一个比较），把小的放前面。之后i+1，也就是选择前三个数，再循环比较一遍，然后继续i+1向前循环。最终比较完成！