（算法设计技巧与分析）MergeSort

#include<iostream>
#include<time.h>
using namespace std;
void merge(int a[],int first,int mid,int end);
void mergeSort(int a[],int low,int high);
int main()
{
int a[11];
srand((unsigned int(time(NULL))));//导入时间种子加每次运行结样试下伪随机数种子
for (int i=0;i<11;i++)
a[i]=rand();
mergeSort(a,0,10);
for(int i=0;i<11;i++)
cout<<a[i]<<" ";
}
void merge(int a[],int first,int mid,int end)//a[first]~a[mid]和a[mid+1]~a[end]已经排序
{
int *parray=new int[end+1];//新数组
int pbotton=first;
int f=first,m=mid;
while(f<mid&&m<=end)
{
if(a[f]<a[m])
{
parray[pbotton]=a[f];
f++;
}
else
{
parray[pbotton]=a[m];
m++;
}
pbotton++;
}
if(f==mid)
{
while(m<=end)
{
parray[pbotton]=a[m];
pbotton++;m++;
}
}
else
{
while(f<mid)
{
parray[pbotton]=a[f];
pbotton++;f++;
}
}
for(int i=first;i<=end;i++)//重新赋值
a[i]=parray[i];
}
void mergeSort(int a[],int low,int high)
{
if(low<high)
{
mergeSort(a,low,(low+high)/2);
mergeSort(a,(low+high)/2+1,high);
merge(a,low,(low+high)/2+1,high);
}
}