常见的排序算法整理

 1 public void insertSort(int[] arr){
 2     int n = arr.length;
 3     for(int i =1;i<n;i++)
 4     {
 5         int value = arr[i];
 6         int j; 
 7         for(j= i; j>0 && value < arr[j-1];j--)
 8         {
 9           arr[j]  = arr[j-1];  
10         }
11         arr[j] = value;
12     }
13 }

 1 public void bubbleSort(int[] arr){
 2     int n = arr.length;
 3     for (int i=0;i<n;i++){
 4         for (int j=0;j<n-i-1;j++){
 5             if(arr[j]>arr[j+1]){
 6                 int t = arr[j+1];
 7                 arr[j+1] = arr[j];
 8                 arr[j] = t;
 9             }
10         }
11     }
12 }

public void shellSort(int[] arr){
    int n =arr.length;
    for (int gap = n/2;gap>0;gap = gap/2){
        for (int i=gap;i<n;i++){
            int j;
            int value = arr[i];
            for (j=i-gap;j>=0&&arr[j]>value;j-=gap){
                arr[j+gap] = arr[j];
            }
            arr[j+gap] = value;
        }
    }
}

public void selectSort(int[] arr){
    int n = arr.length;
    for (int i=0;i<n-1;i++){
        int position = i;
        for (int j=i+1;j<n;j++){
            if(arr[j]<arr[position]){
                position = j;
            }
        }
        int temp = arr[position];
        arr[position] = arr[i];
        arr[i] = temp;
    }
}

 1 public static void quickSort(int[] arr,int left,int right){
 2     //假设将right作为基准
 3     if (left>right)return;
 4 
 5     int index = left;
 6     for (;left<right;left++){
 7         if (arr[left]<arr[right]){
 8             int temp = arr[left];
 9             arr[left] = arr[index];
10            arr[index++] = temp;
11         }
12     }
13 
14     if (index!=right){
15         int temp = arr[right];
16         arr[right] = arr[index];
17         arr[index] = temp;
18     }
19 
20     quickSort(arr,0,index-1);
21     quickSort(arr,index+1,right);
22 }

 1 public void mergeSort(int[] arr,int start,int end){
 2     if (start>=end)return;
 3 
 4     int mid =start+ (end-start)/2;
 5     mergeSort(arr,start,mid);
 6     mergeSort(arr,mid+1,end);
 7 
 8     merge(arr,start,mid,end);
 9 }
10 
11 public static void merge(int[] arr,int start,int mid ,int end){
12     int[] temp = new int[end-start+1];
13     int i=0;
14     int p = start;
15     int q = mid+1;
16     while ( p <= mid && q<=end ){
17         temp[i++] = arr[p]<=arr[q]?arr[p++]:arr[q++];
18     }
19 
20     if(p>mid){
21         while (q<=end){
22             temp[i++] = arr[q++];
23         }
24     }else {
25         while (p<=mid){
26             temp[i++] = arr[p++];
27         }
28     }
29 
30     for ( i =0;i<temp.length;i++){
31         arr[start+i] = temp[i];
32     }
33 
34 }

 1 public static void heapSort(int[] arr){
 2     int n = arr.length-1;
 3     while (n>0){
 4         buildHeap(arr,n);
 5         swap(arr,n,0);
 6         n--;
 7     }
 8 }
 9 
10 public static void buildHeap(int[] a ,int n)
11 {
12     for(int i = (n-1)/2;i>=0;i--)  //叶子节点没有子树，所以不需要比较
13     {
14         heapify(a,n,i);
15     }
16 }
17 
18 public static void heapify(int[] a, int n,int i)
19 {
20     while(true)
21     {
22         int maxPosition = i;
23         if((i*2+1 <= n) && a[i] < a[i*2+1] ) maxPosition = i*2+1;
24         if((i*2+2 <= n ) && a[maxPosition] < a[i*2+2] ) maxPosition = i*2+2;
25         if(maxPosition == i ) break;
26         swap(a,i,maxPosition);
27         i = maxPosition;
28     }
29 }
30 
31 public static void swap(int[] arr,int n,int i){
32     int temp = arr[n];
33     arr[n] = arr[i];
34     arr[i] =temp;
35 }