初级排序算法

选择排序

• 动画演示
  

• 代码实现

public class selectSort { public static void main(String[] args) { int[] nums = {1,5,6,2,3,4,7,8,9}; selectSort(nums); for (int num:nums){             System.out.print(num); } } private static void selectSort(int[] nums){ for (int i = 0;i<nums.length;i++){ int minIndex = i; for (int j = i+1;j<nums.length;j++){ if(nums[minIndex]>nums[j]){                     minIndex = j; } } swap(nums,i,minIndex); } } private static void swap(int[] nums,int index1,int index2){ int temp = nums[index1];         nums[index1] = nums[index2];         nums[index2] = temp; } } 

插入排序

• 动画演示
  
• 代码实现

public class insertSort { public static void main(String[] args) { int[] nums = {1,5,6,2,3,4,7,8,9}; insertSort(nums); for (int num:nums){             System.out.print(num); } } private static void insertSort(int[] nums){ int len = nums.length; for(int i = 1;i<len;i++){ for(int j=i;j>0;j--){ if(nums[j-1]>nums[j]){ swap(nums,j-1,j); }else{ break; } } } } private static void swap(int[] nums,int index1,int index2){ int temp = nums[index1];         nums[index1] = nums[index2];         nums[index2] = temp; } } 

• 优化版本

void insertSort1(int[] nums){ int len = nums.length; for(int i = 1;i<len;i++){ int temp = nums[i]; int j = i-1; while (j>=0 && nums[j]>temp){                nums[j+1] = nums[j];                j--; }            nums[j+1] = temp; } } 

希尔排序

• 动画演示
  

• 代码实现

public class ShellSort { public static void main(String[] args) { int[] nums = {1,5,6,2,3,4,7,8,9}; shellSort(nums); for (int num:nums){             System.out.print(num); } } private static void shellSort(int[] nums){ int len = nums.length; int dalta = len/2; while (dalta>=1){ for(int i = len-1;i>=len-dalta;i--){ for(int j = i;j>=dalta;j-=dalta){ if(nums[j-dalta]>nums[j]){ swap(nums,j-dalta,j); } } }             dalta /=2; } } private static void swap(int[] nums,int index1,int index2){ int temp = nums[index1];         nums[index1] = nums[index2];         nums[index2] = temp; } } 

冒泡排序

• 动画演示
  
• 代码实现

public class bubbleSort { public static void main(String[] args) { int[] nums = {1,5,6,2,3,4,7,8,9}; bubbleSort(nums); for (int num:nums){             System.out.print(num); } } private static void bubbleSort(int[] nums){ int len = nums.length; for(int i = 0;i<len;i++){ boolean flag = true; for (int j = 0;j<len-i-1;j++){ if(nums[j]> nums[j+1]){ swap(nums,j+1,j);                     flag = false; } } if(flag) break; } } private static void swap(int[] nums,int index1,int index2){ int temp = nums[index1];         nums[index1] = nums[index2];         nums[index2] = temp; } } 

高级排序算法

归并排序

• 动画演示
  
• 代码实现

public class megerSort { public static void main(String[] args) { int arr[] = { 8, 4, 5, 7, 1, 3, 6, 2, 9 }; int temp[] = new int[arr.length]; //归并排序需要一个额外空间 mergeSort(arr, 0, arr.length - 1, temp);          System.out.println("归并排序后=" + Arrays.toString(arr)); } private static void mergeSort(int[] arr, int left, int right, int[] temp) { if(left>=right){ return; } int mid = left + (right-left)/2; //向左边递归分解 mergeSort(arr,left,mid,temp); //向右边递归分解 mergeSort(arr,mid+1,right,temp); //合并 merge(arr,left,mid,right,temp); } private static void merge(int[] arr, int left, int mid, int right, int[] temp) { int i = left; int j = mid + 1; int t = 0; while (i<=mid && j<=right){ if(arr[i]<=arr[j]){                 temp[t] = arr[i];                 t++;                 i++; }else{                 temp[t] = arr[j];                 t++;                 j++; } } while (i<=mid){             temp[t] = arr[i];             t++;             i++; } while (j<=right){             temp[t] = arr[j];             t++;             j++; }           t = 0; int tempLeft = left; while (tempLeft<=right){             arr[tempLeft] = temp[t];             tempLeft++;             t++; } } } 

快速排序

• 动画演示
  

• 代码实现

public class quickSort { public static void main(String[] args) { int[] nums = {1,5,2,6,4,7,8,9,-1,-2}; quickSort(nums,0,nums.length-1);         System.out.println(Arrays.toString(nums)); } private static void quickSort(int[] nums,int left,int right){ int l = left; int r = right; int mid = left + (right-left)/2; int privot = nums[mid]; while (l<r){ while (nums[l]<privot){                 l++; } while (nums[r]>privot){                 r--; } if(l>=r){ break; } swap(nums,l,r); if (nums[l]==privot){                 r--; } if(nums[r]==privot){                 l++; } } if(l==r){             l++;             r--; } if (left<r){ quickSort(nums,left,r); } if (right>l){ quickSort(nums,l,right); } } private static void swap(int[] nums,int index1,int index2){ int temp = nums[index1];         nums[index1] = nums[index2];         nums[index2] = temp; } } 

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