归并排序

#include <iostream>
using namespace std;
int tem[1005];
int a[1005];
bool com1(int x,int y)
{
    return x >= y;
}
bool com2(int x ,int y)
{
    return x <=y;
}
void merges(int from[] , int to[],int b ,int m, int e , bool com(int x,int y))
{
    int i = b;
    int j = m+1;
    int k = b;
    while (i<=m&&j<=e)
    {
        if (com(from[i],from[j]))
            to[k++] = from[i++];
        else to[k++] = from[j++];
    }
    for (int t = i; t<=m;) to[k++] = from[t++];
    for (int t = j; t<=e;) to[k++] = from[t++];
    for (int t = b; t <= e ;t++)
        from[t] = to[t];
}
void mergesort(int a[], int b, int e,bool com(int x,int y))
{
    if (b >= e ) return;
    int mid = (b+e)/2;
    mergesort(a,b,mid,com);
    mergesort(a,mid+1,e,com);
    merges(a,tem,b,mid,e,com);
}
void print(int a[],int n)
{
    for (int i = 1; i<= n; i++)
    {
        cout << a[i] <<" ";
    }
    cout << endl;
}
int main()
{
    int n;
    cin >> n;
    for (int i = 1 ; i<= n; i++)
        cin >> a[i];
    mergesort(a,1,n,com1);
    print(a,n);
    mergesort(a,1,n,com2);
    print(a,n);
}

#include <iostream>
using namespace std;
int tem[1005];
int a[1005];
bool com1(int x,int y)
{
    return x >= y;
}
bool com2(int x ,int y)
{
    return x <=y;
}
void merges(int from[] , int to[],int b ,int m, int e , bool com(int x,int y))
{
    int i = b;
    int j = m+1;
    int k = b;
    while (i<=m&&j<=e)
    {
        if (com(from[i],from[j]))
            to[k++] = from[i++];
        else to[k++] = from[j++];
    }
    for (int t = i; t<=m;) to[k++] = from[t++];
    for (int t = j; t<=e;) to[k++] = from[t++];
}
//倍增法归并
void mergesort(int a[], int b, int e,bool com(int x,int y))
{
    int l = 1;
    int L = e-b+1; //长度
    while (l <= L)
    {
        int i;
        for (i = b; i+2*l-1 <= e; i+=2*l)
        {
            merges(a,tem,i,i+l-1,i+2*l-1,com);
        }
        merges(a,tem,i,min(i+l-1,e),e,com);
        l *= 2;
        // 循环数组
        for (i = b; i+2*l-1 <= e; i+=2*l)
        {
            merges(tem,a,i,i+l-1,i+2*l-1,com);
        }
        merges(tem,a,i,min(i+l-1,e),e,com);
        l *= 2;
    }
}
void print(int a[],int n)
{
    for (int i = 1; i<= n; i++)
    {
        cout << a[i] <<" ";
    }
    cout << endl;
}
int main()
{
    int n;
    cin >> n;
    for (int i = 1 ; i<= n; i++)
        cin >> a[i];
    mergesort(a,1,n,com1);
    print(a,n);
    mergesort(a,1,n,com2);
    print(a,n);
}

#include <iostream>
using namespace std;
bool com1(int x,int y)
{
    return x >= y;
}
bool com2(int x ,int y)
{
    return x <=y;
}
struct list_
{
    int v;
    int next;
}a[1005];
int merge_list(list_ a[],int first ,int second ,bool com(int x ,int y),int n)
{
    int new_head = n+1;
    int * ptr;
    while (first!=-1 && second != -1)
    {
        if (com(a[first].v,a[second].v))
            ptr = &first;
        else
            ptr = &second;
        a[new_head].next = (*ptr);
        new_head = (*ptr);
        (*ptr) = a[(*ptr)].next;
    }
    a[new_head].next = first + second + 1;
    return a[n+1].next;
}
int mergesort(list_ a[], int b, int e ,bool com(int x,int y),int n)
{
    if (b == e) return b;
    if (b > e ) return -1;
    int mid = (e+b)/2;
    int first = mergesort(a,b,mid,com,n);
    int second = mergesort(a,mid+1,e,com,n);
    return merge_list(a,first,second,com,n);
}
void print(list_ a[],int n,int head)
{
    for (int i = head; i != -1; i = a[i].next)
    {
        cout << a[i].v <<" ";
    }
    cout << endl;
}
void init(int n)
{
    for (int i = 1; i<=n;i++)
        a[i].next = -1;
}
int main()
{
    int n;
    cin >> n;
    for (int i = 1 ; i<= n; i++)
        cin >> a[i].v;
    init(n);
    int head = mergesort(a,1,n,com1,n);
    print(a,n,head);
    init(n);
    head = mergesort(a,1,n,com2,n);
    print(a,n,head);
}