How many points for seeking a point which is a point inside the lower left corner of the lower right corner of the rectangle formed by each of x and y is no point is different
Start thinking:
First performed in accordance with the x-coordinate cdq divide and conquer sorting
Then y in the sort cdq enumeration mid + 1-r of the upper right corner point as
Maintenance found a monotonically increasing as long as the left half of the points can be formed with a monotonous stack well maintained
But it ignores the impact of the right half has traversed point answers generated
Reference yyb giant guy: https://www.cnblogs.com/cjyyb/p/8419102.ht
Think about the new left point x can be found to affect relations
#include<bits/stdc++.h> using namespace std; #define rep(i,a,b) for(int i=(a);i<=(b);i++) #define repp(i,a,b) for(int i=(a);i>=(b);--i) #define ll long long #define see(x) (cerr<<(#x)<<'='<<(x)<<endl) #define inf 0x3f3f3f3f #define CLR(A,v) memset(A,v,sizeof A) ///////////////////////////////////// const int N=1e6+10; //维护单调递减的单调栈 int n,m;ll ans[N];ll sum; struct node{int x,y,id;}s[N]; bool cmp(node a,node b){return a.y>b.y;} bool cmpx(node a,node b){return a.x<b.x;} int sta1[N],top1,sta2[N],top2; void cdq(int l,int r) { if(l==r)return ;int mid=(l+r)>>1; cdq(l,mid);cdq(mid+1,r); int j=mid+1; sort(s+l,s+mid+1,cmp);sort(s+mid+1,s+r+1,cmp); int top1=top2=0; rep(i,l,mid) { while(j<=r&&s[i].y<s[j].y) { while(top1>0&&s[sta1[top1]].x>s[j].x)top1--; sta1[++top1]=j++; } while(top2>0&&s[sta2[top2]].x<s[i].x)top2--; sta2[++top2]=i; if(top2==1)sum+=1ll*top1; else { int L=1,R=top1,an=top1+1; while(L<=R) { int mid=(L+R)>>1; if(s[sta1[mid]].y>s[sta2[top2-1]].y)L=mid+1; else an=mid,R=mid-1; } sum+=1ll*top1-an+1; } } } int main() { cin>>n; rep(i,1,n) { scanf("%d%d",&s[i].x,&s[i].y);s[i].id=i; } sort(s+1,s+1+n,cmpx); cdq(1,n); cout<<sum; return 0; }