归并排序

直接给代码 原理就不啰嗦了；

void OutPut(int *arr,int len)
{
    for(int i=0; i < len; ++i)
    {
        cout<<arr[i]<<"  ";
    }
    cout<<endl;
}
//序列a1为两个有序的子序列，a1[s...m] 和 a[m+1,e]有序
// 把a1的两个有序子序列合并为一个有序数列a2
void Merge(int* a1,int* a2, int s, int m, int e)
{
    int k,j;
    for(k = s, j = m+1; s <= m && j <= e; ++k)
    {
        if(a1[s] < a1[j])
        {
            a2[k] = a1[s++];
        }
        else
        {
            a2[k] = a1[j++];
        }
     }
    if(s <= m)
    {
        for(int i = 0; i <= m-s; ++i)
        {
            a2[k+i] = a1[s+i];
        }
    }
    if(j <= e)
    {
        for(int l = 0; l <= e-j; ++l)
        {
            a2[k+l] = a1[j+l];
        }
    }
}
//归并排序里的Msort函数
void Msort(int* a1,int* a2,int b, int e)
{
    int atmp[21];
    int m;
    if(b == e) a2[b] = a1[b];
    else
    {
         m = (e + b)/2;
        Msort(a1,atmp,b,m);
        Msort(a1,atmp,m+1,e);
        Merge(atmp,a2,b,m,e);
    }
}
//归并排序入口
void MergeSort(int *arr,int len)
{
    Msort(arr,arr,0,len-1);
}
int _tmain(int argc, _TCHAR* argv[])
{
    int a[20]={-1,23,5456,21,784,12,46,89,21213,687,32,-12,8,0,123,-34,2332,33330,5674,1111};
    HeapSort(a,20);
//    MergeSort(a,20);
    OutPut(a,20);
    return 0;
}