八大排序算法总结（2）

 1 //merge sort
 2     public static void merge(int[] a,int aux[],int lo ,int mid,int hi ){
 3         int i = lo;
 4         int j = mid+1;
 5         //copy a
 6         for (int k = lo; k <= hi; k++) 
 7             aux[k] = a[k];
 8         //merge
 9         for(int k = lo;k<=hi;k++){        
10             //先判断是否越界
11             if(i>mid)                    a[k]=aux[j++];
12             else if(j>hi)                a[k]=aux[i++];
13             // merge
14                 else if(aux[j]<=aux[i])     a[k]=aux[j++];
15                 else                     a[k]=aux[i++];
16         }
17     }
18     public static void mergesort(int[] a,int aux[],int lo,int hi) {
19         //边界条件
20                 if(lo>=hi) return ;
21         int mid = (hi-lo)/2+lo;
22         mergesort(a,aux, lo, mid);
23         mergesort(a,aux, mid+1, hi);
24         merge(a,aux, lo, mid, hi);
25         
26     }
27     public static void mergeSort(int[] a){
28         int aux[] = new int[a.length];
29         mergesort(a,aux, 0, a.length-1);
30     }

 1 //quick sort
 2     //partion
 3     private static int partion(int[] a ,int lo,int hi) {
 4         int v = a[lo];
 5         int i = lo ,j=hi+1;
 6         while(true){
 7             while(a[++i]<v) if(i>=hi) break;
 8             while(a[--j]>v) if(j<=lo) break;
 9             if(i>=j) break;
10             swap(a, i, j);
11         }
12         swap(a, lo, j);
13         return j;
14     }
15     public static void partionsort(int[] a,int lo,int hi) {
16         if(lo>=hi) return;
17         int j = partion(a, lo, hi);
18         partionsort(a, lo, j);
19         partionsort(a, j+1, hi);
20         
21     }
22     public static void partionSort(int[] a) {
23         partionsort(a, 0, a.length-1);
24     }
25