排序方法汇总（三）归并排序

 1 #include <iostream>
 2 using std::cout;
 3 
 4 void gsort(int *a,int front,int rear)
 5 {
 6     if(front>=rear)return;//边界处理
 7     if(front+1==rear)//边界处理
 8     {
 9         if(a[rear]<a[front])
10         {int temp=a[front];a[front]=a[rear];a[rear]=a[front];}
11         return;
12     }
13     int m=(front+rear)/2;
14     gsort(a,front,m);
15     gsort(a,m+1,rear);
16     int *p=new int[rear-front+1];//开辟新的空间，将左右两组排序到新空间
17     int pp=0,p1=front,p2=m+1;
18     while(1)
19     {
20         if(p1>m && p2>rear)break;
21         if(( a[p1]<a[p2] || p2>rear) && p1<=m )p[pp++]=a[p1++];
22         else p[pp++]=a[p2++];
23     }
24     for(int i=0;i<rear-front+1;i++)a[i+front]=p[i];
25     delete[] p;
26 }
27 
28 int main()
29 {
30     int a[]={11,5,51,0,531,5,-1,46,4,-5,65,4};
31     int len=sizeof(a)/sizeof(int);
32     gsort(a,0,len-1);
33     for(int i=0;i<len;i++)cout<<a[i]<<" ";
34     cout<<"\n";
35 
36     return 0;
37 }