为什么50分？

lucy2012 @ 2024-06-05 21:18:58

#include<bits/stdc++.h>
using namespace std;
int a[1000010],b[1000010],n,ans;
void merge(int l,int r){
    int i,j,k,mid;
    i=l;
    mid=(l+r)/2;
    j=mid+1;
    k=l;
    while(i<=mid&&j<=r){
        if(b[i]<=b[j])
            a[k++]=b[i++];
        else{
            a[k++]=b[j++];
            ans+=mid-i+1;
        }
    }
    while(i<=mid)
        a[k++]=b[i++];
    while(j<=r)
        a[k++]=b[j++];
    for(i=l;i<=r;i++)
        b[i]=a[i];
}
void mergesort(int l,int r){
    if(l<r){
        int mid=(l+r)/2;
        mergesort(l,mid);
        mergesort(mid+1,r);
        merge(l,r);
    }
} 
int main(){
    cin>>n;
    for(int i=1;i<=n;i++)
        cin>>b[i];
    mergesort(1,n);
    cout<<ans;
    return 0;
}    

by wjr_jok @ 2024-06-05 21:30:04

@lucy2012

#include<bits/stdc++.h>
using namespace std;
#define int long long
int a[1000010],b[1000010],n,ans;
void merge(int l,int r){
    int i,j,k,mid;
    i=l;
    mid=(l+r)/2;
    j=mid+1;
    k=l;
    while(i<=mid&&j<=r){
        if(b[i]<=b[j])
            a[k++]=b[i++];
        else{
            a[k++]=b[j++];
            ans+=mid-i+1;
        }
    }
    while(i<=mid)
        a[k++]=b[i++];
    while(j<=r)
        a[k++]=b[j++];
    for(i=l;i<=r;i++)
        b[i]=a[i];
}
void mergesort(int l,int r){
    if(l<r){
        int mid=(l+r)/2;
        mergesort(l,mid);
        mergesort(mid+1,r);
        merge(l,r);
    }
} 
signed main(){
    cin>>n;
    for(int i=1;i<=n;i++)
        cin>>b[i];
    mergesort(1,n);
    cout<<ans;
    return 0;
}    

by wjr_jok @ 2024-06-05 21:30:20

@lucy2012 十年OI一场空，__。

by lucy2012 @ 2024-06-05 21:30:52

@wjr_jok wssb

by __little__Cabbage__ @ 2024-07-04 11:02:55

@wjr_jok 不开long long见祖宗！