bzoj4237稻草人

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 int read()
 4 {
 5    int x=0,f=1;char ch=getchar();
 6    while (ch<‘0‘||ch>‘9‘) {if (ch==‘-‘) f=-1;ch=getchar();}
 7    while (ch>=‘0‘&&ch<=‘9‘) x=(x<<1)+(x<<3)+ch-‘0‘,ch=getchar();
 8    return x*f;
 9 }
10 const int N=200005;
11 int n,q1[N],q2[N];
12 long long ans;
13 struct node{int x,y;}a[N],tmp[N];
14 bool cmp(const node &A,const node &B) {return A.y<B.y;}
15 int find(int x,int l,int r)
16 {
17    while (l+1<r)
18    {
19          int mid=(l+r)/2;
20       if (a[q2[mid]].x<x) l=mid;else r=mid;//边界上的点不算 
21    }
22    return l;
23 }
24 void solve(int l,int r)
25 {
26     if (l==r) return;
27     int mid=((l+r)>>1);
28     solve(l,mid);solve(mid+1,r);
29     int top1=0,top2=0;
30     for (int i=mid+1,j=l;i<=r;i++)
31     {
32       while (top1&&a[i].y<a[q1[top1]].y) top1--;
33       for (;j<=mid&&a[j].x<a[i].x;j++)//勿取等号，一条线不算矩形 
34       {
35            while (top2&&a[j].y>a[q2[top2]].y) top2--;
36            q2[++top2]=j;
37       }
38       ans+=top2-find(a[q1[top1]].x,0,top2+1);//二分边界注意 
39       q1[++top1]=i;
40     }
41     int L=l,R=mid+1;
42     for (int i=l;i<=r;i++)
43       if (R>r||a[L].x<a[R].x&&L<=mid) tmp[i]=a[L++];else tmp[i]=a[R++];
44     for (int i=l;i<=r;i++) a[i]=tmp[i];
45 }
46 int main()
47 {
48     n=read();
49     for (int i=1;i<=n;i++) a[i].x=read(),a[i].y=read();
50     sort(a+1,a+n+1,cmp);
51     solve(1,n);
52     printf("%lld\n",ans);
53     return 0;
54 }