BZOJ1106: [POI2007]立方体大作战tet

#include<set>
#include<map>
#include<deque>
#include<queue>
#include<stack>
#include<cmath>
#include<ctime>
#include<bitset>
#include<string>
#include<vector>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<climits>
#include<complex>
#include<iostream>
#include<algorithm>
#define ll long long
#define inf 1e9
#define lowbit(x) x&(-x)
using namespace std;

const int maxn = 101000;

int n,N;
int a[maxn];
int s[maxn];
void add(int x,int c){for(;x<=n;x+=lowbit(x))s[x]+=c;}
int query(int x){int re=0;for(;x;x-=lowbit(x))re+=s[x];return re;}

int las[maxn];

int main()
{
scanf("%d",&N); n=N<<1;
int re=0;
for(int i=1;i<=n;i++)
{
int x; scanf("%d",&x); a[i]=x;
if(!las[x]) las[x]=i;
else
{
re+=i-las[x]+query(las[x])-1;
add(1,-1); add(las[x],1);
add(1,-1); add(i,1);
}
}
printf("%d\n",re);

return 0;
}