【BZOJ】【P1106】【POI2007】【立方体大作战tet】【题解】【树状数组】

传送门：http://www.lydsy.com/JudgeOnline/problem.php?id=1106

POI一刷根本停不下来……

树状数组统计相同元素之间不能匹配的个数

Code:

#include<bits/stdc++.h>using namespace std;const int maxn=1e5+10;int n,ans;int d[maxn],a[maxn];int p[maxn][2],vis[maxn];int lowbit(int x){return x&-x;}int get(int x){int ans=0;while(x)ans+=d[x],x-=lowbit(x);return ans;}void updata(int x,int s){while(x<=n)d[x]+=s,x+=lowbit(x);}int main(){scanf("%d",&n);n*=2;for(int i=1;i<=n;i++)scanf("%d",&a[i]);for(int i=1;i<=n;i++){if(!vis[a[i]])updata(i,1),vis[a[i]]=i;else{ans+=get(i)-get(vis[a[i]]-1)-1;updata(vis[a[i]],-1);}}cout<<ans<<endl;return 0;}