归并排序——最省时的排序

/*
因为归并排序至于O（n）的复杂度所以省时
*/
#include<iostream>
#include<stdio.h>
#include<string.h>
#include<string>
#include<algorithm>
#include<vector>
#include<map>

#define N 100010
#define MAXN 100010

using namespace std;

//将有二个有序数列a[first...mid]和a[mid...last]合并。
void mergearray(int a[], int first, int mid, int last, int temp[])
{
    int i = first, j = mid + 1;
    int m = mid,   n = last;
    int k = 0;
    while (i <= m && j <= n)    
    {
        if (a[i] <= a[j])
            temp[k++] = a[i++];
        else
            temp[k++] = a[j++];
    }
    
    while (i <= m)
        temp[k++] = a[i++];
    
    while (j <= n)
        temp[k++] = a[j++];
    
    for (i = 0; i < k; i++)
        a[first + i] = temp[i];
}
void mergesort(int a[], int first, int last, int temp[])
{
    if (first < last)
    {
        int mid = (first + last) / 2;
        mergesort(a, first, mid, temp);    //左边有序
        mergesort(a, mid + 1, last, temp); //右边有序
        mergearray(a, first, mid, last, temp); //再将二个有序数列合并
    }
}

bool MergeSort(int a[], int n)
{
    int *p = new int[n];
    if (p == NULL)
        return false;
    mergesort(a, 0, n - 1, p);
    delete[] p;
    return true;
}

int main()
{
    //freopen("C:\Users\acer\Desktop\in.txt","r",stdin);
    int cur1[]={1,4,7,8,5,2,3,6,9,0};
    int cur2[12];
    mergesort(cur1, 0, 9, cur2);
    for(int i=0;i<10;i++)
        cout<<cur2[i]<<" ";
    cout<<endl;
    
    return 0;
}