归并排序

归并排序具有递归和非递归两种方式：

递归的归并排序代码如下：

#include <iostream>
#include <list>
#include <stack>
using namespace std;
//合并排序的前期判断，将不符合归并排序的数组进行筛除，
//申请归并排序的辅助数组空间
void MergeSort(int *p, int n)
{
    void Msort(int *p, int *temp,int left, int right);
    if(n <= 0 || p == NULL)
        return;
    int *temp = new int[n];
    if(temp == NULL)
        return;
    Msort(p, temp, 0, n-1);
    delete [] temp;
}
//递归形式的合并排序
void Msort(int *p, int *temp, int left, int right)
{
    void Merge(int *, int *, int, int, int);
    if(left < right)
    {
        int leftend = (left + right) / 2;
        int rightbegin = leftend + 1;
        Msort(p, temp, left, leftend);
        Msort(p, temp, rightbegin, right);
        Merge(p, temp,left, rightbegin, right);
    }
}
//将数组中指定长度的两段，按照一定大小进行合并。
void Merge(int *p, int *temp, int left, int rightbegin, int right)
{
    int TempArray = rightbegin;
    int pos = left;
    int begin = left;
    while(left < TempArray && rightbegin <= right)
    {
        if(p[left] <= p[rightbegin])
            temp[pos++] = p[left++];
        else
            temp[pos++] = p[rightbegin++];
    }
    while(left < TempArray)
        temp[pos++] = p[left++];
    while(rightbegin <= right)
        temp[pos++] = p[rightbegin++];
    while(pos-- >= begin)
        p[pos] = temp[pos];
}

int main()
{
    //测试
    int num = 9;
    int *p = new int[num];
    for(int i = 0; i < num; i++)
        p[i] = 10 - i;
    for(int i = 0; i < num; i++)
        cout << p[i] << endl;
    MergeSort(p,num);
    for(int i = 0; i < num; i++)
        cout << p[i] << endl;
    return 0;
}