排序算法总结2

归并排序：

void merge(int *a,int *b ,int left,int right)
{
int l = left;
int r = right+1;
4000
int m = (left+right)/2;
int k = m+1;
int i = left;
while (l<(m+1)&&k<r)
{
if (a[l]<a[k])
{
b[i] = a[l];
i++;
l++;
}
else
{
b[i] = a[k];
i++;
k++;
}
}
if (k>=r)
{
while (l<(m+1))
{
b[i] = a[l];
i++;
l++;
}
}
else
{
while (k<r)
{
b[i] = a[k];
i++;
k++;
}
}
for (int i = left;i<=right;i++)
{
a[i] = b[i];
}
}

void merge_sort(int * a,int * b,int left,int right)
{
if (left < right)
{
int middle = (left+right)/2;
merge_sort(a,b,left,middle);
merge_sort(a,b,middle+1,right);
merge(a,b,left,right);
}
}

int main()
{
int a[10] = {9,2,8,3,5,7,6,1,4,10};
int b[10]={0};
merge_sort(a,b,0,9);
for (int i=0;i<10;i++)
{
cout<<a[i]<<" ";
}
return 0;
}

平均时间复杂度：nlogn
额外空间：n

稳定性：稳定

比较操作的次数介于(nlogn) / 2和nlogn - n + 1