test/AOJ_ALDS1_5_D.test.cpp

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Last update: 2023-04-05 23:10:22+09:00
Problem: http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ALDS1_5_D

Depends on

Code

#define PROBLEM "http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ALDS1_5_D"

#include "../template.hpp"

#include "../DP/InversionNumber.hpp"

signed main(){
    int n;cin>>n;
    vector<int> a(n);
    cin>>a;
    cout<<InversionNumber(a)<<endl;
    return 0;
}

#line 1 "test/AOJ_ALDS1_5_D.test.cpp"
#define PROBLEM "http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ALDS1_5_D"

#line 1 "template.hpp"
#include<bits/stdc++.h>
using namespace std;
#define ALL(x) begin(x),end(x)
#define rep(i,n) for(int i=0;i<(n);i++)
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define mod 1000000007
using ll=long long;
const int INF=1000000000;
const ll LINF=1001002003004005006ll;
int dx[]={1,0,-1,0},dy[]={0,1,0,-1};
// ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return true;}return false;}

struct IOSetup{
    IOSetup(){
        cin.tie(0);
        ios::sync_with_stdio(0);
        cout<<fixed<<setprecision(12);
    }
} iosetup;
 
template<typename T>
ostream &operator<<(ostream &os,const vector<T>&v){
    for(int i=0;i<(int)v.size();i++) os<<v[i]<<(i+1==(int)v.size()?"":" ");
    return os;
}
template<typename T>
istream &operator>>(istream &is,vector<T>&v){
    for(T &x:v)is>>x;
    return is;
}

#line 4 "test/AOJ_ALDS1_5_D.test.cpp"

#line 1 "DP/InversionNumber.hpp"
template<typename T>
long long InversionNumber(vector<T> v){
    vector<T> ord=v;
    sort(begin(ord),end(ord));
    ord.erase(unique(begin(ord),end(ord)),end(ord));
    vector<long long> bit(ord.size()+1,0);
    long long ret=0;
    for(int i=0;i<(int)v.size();i++){
        int p=lower_bound(begin(ord),end(ord),v[i])-begin(ord)+1;
        for(int j=p;j;j-=(j&-j)) ret-=bit[j];
        for(int j=p;j<=(int)ord.size();j+=(j&-j)) bit[j]+=1;
        ret+=i;
    } 
    return ret;
}
#line 6 "test/AOJ_ALDS1_5_D.test.cpp"

signed main(){
    int n;cin>>n;
    vector<int> a(n);
    cin>>a;
    cout<<InversionNumber(a)<<endl;
    return 0;
}