归并排序模板

#include <cstdio>
#include <cstdlib>
#include <iostream>
#define N 30100
using namespace std;

int ans;
void Merge(int a[],int low,int mid,int high)
{
    int * b = (int *)malloc((high-low+1)*sizeof(int));
    int k = 0;
    int begin1 = low;
    int end1 = mid;
    int begin2 = mid + 1;
    int end2 = high;
    while(begin1 <= end1 && begin2 <= end2)
    {
        if(a[begin1] <= a[begin2])
            b[k++] = a[begin1++];
        else
            b[k++] = a[begin2++];
    }
    if(begin1 <= end1)
        for(int q = begin1; q <= end1; q++)
            b[k++] = a[q];
    else
        for(int q = begin2; q <= end2; q++)
            b[k++] = a[q];
    for(int i=0; i<k; i++)
        a[low+i] = b[i];
    free(b);
}

void merge_sort(int arr[],int first,int last)
{
    int mid = 0;
    if(first < last)
    {
        mid = (first + last) / 2;
        merge_sort(arr,first,mid);
        merge_sort(arr,mid + 1,last);
        Merge(arr,first,mid,last);
    }
}

int main()
{
    int n;
    int s[N];
    scanf("%d",&n);
    for(int i=0;i<n;i++)
        scanf("%d",&s[i]);
    merge_sort(s,0,n-1);
    for(int i=0;i<n;i++)
        printf("%d%c",s[i],i==n-1?'\n':' ');
}