归并排序模板

【代码】

归并排序模板

#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdio>
#include<cmath>
#include<set>
using namespace std;
#define f(i,n) for(int i=1;i<=(n);i++)
#define ll long long
#define INF 1<<30
#define N 100010
#define c 99999997
using namespace std;
int z[N];
int ans;
int n;
int temp[N];
void merge(int l,int m,int r)
{
     int i=l,j=m+1,k=l;
     while(i<=m&&j<=r)
     {
         if(z[i]>z[j])
         {
             temp[k++]=z[j++];
             ans=(ans+m-i+1)%c;
         }
         else temp[k++]=z[i++];
     }
     while(i<=m)temp[k++]=z[i++];
     while(j<=r)temp[k++]=z[j++];
     for(int v=l;v<=r;v++)z[v]=temp[v];
}
void merge_sort(int l,int r)
{
    if(l>=r)return;
    int mid=(l+r)>>1;
    merge_sort(l,mid);
    merge_sort(mid+1,r);
    merge(l,mid,r);
}
int main()
{
    scanf("%d",&n);
    f(i,n)scanf("%d",&z[i]);
    merge_sort(1,n);
    printf("%d",ans);
}