基本思想

　　归并（Merge）排序法是将两个（或两个以上）有序表合并成一个新的有序表，即把待排序序列分为若干个子序列，每个子序列是有序的。然后再把有序子序列合并为整体有序序列。

代码实现

#include<iostream>
using namespace std;

void MergeArray(int Array[], int First, int Middle, int Last, int P[])
{
    int i = First, j = Middle + 1;
    int m = Middle, n = Last;
    int k = 0;

    while (i <= m&&j <= n)
    {
        if (Array[i] <= Array[j])
        {
            P[k] = Array[i];
            ++k; ++i;
        }
        else
        {
            P[k] = Array[j];
            ++k; ++j;
        }
    }

    while (i <= m)//若后一个表被取空
    {
        P[k] = Array[i];
        ++k; ++i;
    }

    while (j <= n)//若前一个表被取空
    {
        P[k] = Array[j];
        ++k; ++j;
    }

    for (int i = 0; i <k; i++)
    {
        Array[First + i] = P[i];
    }
}

void MergeSort(int Array[], int First, int Last, int P[])
{
    if (First < Last)
    {
        int mid = (First + Last) / 2;
        MergeSort(Array, First, mid, P);
        MergeSort(Array, mid + 1, Last, P);
        MergeArray(Array, First, mid, Last, P);
    }
}

int main()
{

    int MyData[10] = { 12,13,16,22,9,14,15,20,23,24 };
    int *Result = new int[10];//存储排序结果
    MergeSort(MyData, 0, 9, Result);
    delete[] Result;

    for (int i = 0; i < 10; i++)
    {
        cout << MyData[i] << " ";
    }
    cout << endl;
    system("pause");
    return 0;
}