归并排序

#include <iostream>
using namespace std;
//将数组 a[low,mid] 与 a(mid,high] 合并（归并）
void Merge(int * a, int low, int mid, int high, int * temp)
{
    int i,j,k;
    i = low;
    j = mid + 1;//避免重复比较a[mid]
    k = 0;
    while (i <= mid && j <= high)//数组a[low,mid]与数组(mid,high]均没有全部归入数组temp中去
    {
        if(a[i] <= a[j])        //如果a[i]小于等于a[j]
            temp[k++] = a[i++]; //则将a[i]的值赋给temp[k]，之后i,k各加一，表示后移一位
        else
            temp[k++] = a[j++]; //否则，将a[j]的值赋给temp[k]，j,k各加一
    }
    while(i <= mid)             //表示数组a(mid,high]已经全部归入temp数组中去了，而数组a[low,mid]还有剩余
        temp[k++] = a[i++];     //将数组a[low,mid]剩下的值，逐一归入数组temp
    while(j <= high)           //表示数组a[low,mid]已经全部归入到temp数组中去了，而数组(mid,high]还有剩余
        temp[k++] = a[j++];     //将数组a(mid,high]剩下的值，逐一归入数组temp
    for (i = 0; i < k; i++)     //将归并后的数组的值逐一赋给数组a[low,high]
        a[low+i] = temp[i];     //注意，应从a[low+i]开始赋值
}
//二路归并（递归实现）
void MergeSort(int * a, int low, int high, int * temp)
{
    if (low < high)
    {
        int mid = (low + high)/2;
        MergeSort(a,low,mid,temp);      //左边有序
        MergeSort(a,mid+1,high,temp);   //右边有序
        Merge(a,low,mid,high,temp);     //再将两个有序序列合并
    }
}
/*----------测试代码----------*/
int main()
{
    int a[] = {2,23,34,43,45,6,7,8,5,4,56,78,80,211,222,444,111};
    int La = sizeof(a)/sizeof(a[0]);
    int * p = new int[La];
    MergeSort(a,0,La-1,p);
    for (int i = 0; i < La; i++)
    {
        cout<<a[i]<<' ';
    }
    cout<<endl;
    delete []p;
}