离散化+树状数组逆序对

这篇只是简单的排序啦

#include<bits/stdc++.h>
using namespace std;
int n,a[10050],ans[10050],tp[10050];
map<int,int> mp;
int main(){
    cin>>n;
    for(int i=1;i<=n;i++) cin>>a[i],tp[i]=a[i];
    sort(tp+1,tp+1+n);
    int m=unique(tp+1,tp+1+n)-(tp+1);
    for(int i=1;i<=m;i++)
        mp[tp[i]]=i; 
    for(int i=1;i<=n;i++)
        ans[i]=mp[a[i]];
    for(int i=1;i<=n;i++) printf("%d ",ans[i]);return 0;
}

 逆序对，在线插入后1，查比自己大的数和即可

#include<bits/stdc++.h>
#define rep(i,x,y) for(register int i=x;i<=y;i++)
using namespace std;
int n,a[10050],ans,c[10050],mx;
inline int lowbit(int x){return x&(-x);}
void change(int x){for(;x<=mx;x+=lowbit(x)) c[x]++;return;}
int sum(int x){int ans=0;for(;x;x-=lowbit(x)) ans+=c[x];return ans;}
int main(){
    freopen("5.in","r",stdin);
    cin>>n;mx=-1;
    rep(i,1,n) cin>>a[i],mx=max(mx,a[i]);
    rep(i,1,n) change(a[i]),ans+=i-sum(a[i]);
    printf("%d",ans);return 0;
}