11、归并排序

/*
归并排序，需要多一倍的内存空间
速度和快速排序一样快
*/

#include<iostream>
#include<algorithm>

using namespace std;

template<class T>
void MergeSort(T *initlist, T *resultlist, const int l, const int m, const int n)
{
    int i1, i2, iresult;
    for (i1 = l, i2 = m + 1, iresult = l; i1 <= m && i2 <= n; iresult++)
    {
        if (initlist[i1] <= initlist[i2])
        {
            resultlist[iresult] = initlist[i1];
            i1++;
        }
        else
        {
            resultlist[iresult] = initlist[i2];
            i2++;
        }
    }
    std::copy(initlist+i1, initlist+ m+1, resultlist+iresult);//将比较完剩下的放进结果数组
    std::copy(initlist+i2, initlist+ n + 1, resultlist+iresult);

}

template<class T>
void MergePass(T *initList,T *resultList,const int n,const int s)
{
    int i;
    for (i = 1; i <= n - 2 * s + 1; i += 2 * s)
    {
        MergeSort(initList,resultList,i,i+s-1,i+2*s-1);
    }
    if ((i + s - 1) < n)//有剩余的
        MergeSort(initList, resultList, i, i + s - 1, n);
    else
        copy(initList + i, initList + n + 1, resultList + i);
}

template <class T>
void Merge(T *a, const int n)
{
    T *tempList = new int[n + 1];//tempList[0]不用
    for (int l = 1; l < n; l *= 2)
    {
        MergePass(a,tempList,n,l);
        l *= 2;
        MergePass(tempList,a,n,l);
    }
    delete[] tempList;//删除临时数组空间，防止内存泄漏
}


int main()
{
    int a[] = { 0,23,47,81,95,7,14,39,55,62,74 };
    int b[11] = { 0 };
    MergeSort(a, b, 1, 4, 10);
    for (int i = 1; i < 11; i++)
    {
        cout << b[i] << " ";
    }
    cout << endl;

    int m[] = {0,26,5,77,1,61,11,59,15,48,19};
    int n[11] = { 0 };
    MergePass(m,n,10,1);
    cout << "第一次归并：" << endl;
    for (int i = 1; i < 11; i++)
        cout << n[i] << " ";
    cout << endl;

    MergePass(n, m, 10, 2);
    cout << "第二次归并：" << endl;
    for (int i = 1; i < 11; i++)
        cout << m[i] << " ";
    cout << endl;

    MergePass(m, n, 10, 4);
    cout << "第三次归并：" << endl;
    for (int i = 1; i < 11; i++)
        cout << n[i] << " ";
    cout << endl;

    MergePass(n, m, 10, 8);
    cout << "第四次归并：" << endl;
    for (int i = 1; i < 11; i++)
        cout << m[i] << " ";
    cout << endl;

    cout << "上面的都是中间结果的测试" << endl;
    cout << "下面开始测试归并排序的最后结果" << endl;
    int x[] = {0,26,5,77,1,61,11,59,15,48,19};
    Merge(x,10);
    for (int i = 1; i < 11; i++)
        cout << x[i] << " ";
    cout << endl;
    system("pause");
    return 0;
}

vs2015中运行结果：