·归并排序模板

#include
using namespace std;
const int N = 1e5 + 10;
int n,q[N],temp[N];
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 k = 0,i = l,j = mid + 1;
    while(i <= mid && j <= r)
    if(q[i] <= q[j]) temp[k++] = q[i++];
    else temp[k++] = q[j++];
    while(i <= mid) temp[k++] = q[i++];
    while(j <= r) temp[k++] = q[j++];
    for(i = l,j = 0;i <= r;i++,j++) q[i] = temp[j];//合并
}
int main()
{
    cin >> n;
    for(int i = 0;i < n;i++) cin >> q[i];
    merge_sort(q,0,n - 1);
    for(int i = 0;i < n;i++) cout << q[i] << ' ';
    return 0;
}

分界点很重要，在合并时要注意一下