归并排序的步骤
- 1.选择中间位置mid
- 2.递归排序
- 3.合并(双指针)
void merge_sort(int q[],int l,int r)
{
if(l >= r) return;
int mid = l + r >> 1;
merge_sort(q,l,mid),merge_sort(q,mid+1,r);
int i = l , j = mid + 1;
int k = 0;
while(i <= mid && j <= r)
{
if(q[i] < q[j]) tmp[k++] = q[i++];
else tmp[k++] = q[j ++ ];
}
while(i <= mid) tmp[k++] = q[i++];
while(j <= r) tmp[k++] = q[i++];
for(int i = l ,j = 0 ; i <= r ; i++ , j++) q[i] =tmp[j];
}