bzoj 2244

没有正确分析路径可能的条数，它是指数增长的，会爆long long。

然后就是正反两次时间分治。

另一个就是max with count，即带计数的最值，即除了记录最值，还要记录最值取得的次数。

 /**************************************************************
     Problem: 2244
     User: idy002
     Language: C++
     Result: Accepted
     Time:4108 ms
     Memory:4520 kb
 ****************************************************************/

 #include <cstdio>
 #include <algorithm>
 #define oo 0x3f3f3f3f
 #define N 50010
 using namespace std;

 typedef bool (*Cmp)( int a, int b );

 struct Point {
     int x, y;
     Point(){}
     Point( int x, int y ):x(x),y(y){}
 };
 struct Info {
     int v;
     long double c;
     Info(){}
     Info( int v, long double c ):v(v),c(c){}
     void add( Info o ) {
         if( o.v>v )
             *this = o;
         else if( o.v==v )
             c += o.c;
     }
 };

 int n;
 Point pts[N];
 Info dp[][N];
 Info bit[N];
 int q[N];
 Cmp cmp;
 int disc[N], dtot;
 long double ans[N];

 bool cmpa( int a, int b ) {
     if( pts[a].x!=pts[b].x ) return pts[a].x<pts[b].x;
     if( pts[a].y!=pts[b].y ) return pts[a].y<pts[b].y;
     return a<b;
 }
 bool cmpb( int a, int b ) {
     if( pts[a].x!=pts[b].x ) return pts[a].x>pts[b].x;
     if( pts[a].y!=pts[b].y ) return pts[a].y>pts[b].y;
     return a<b;
 }
 void modify( int pos, Info o ) {
     if( cmp==cmpb ) pos = dtot+-pos;
     for( int i=pos; i<=dtot; i+=i&-i )
         bit[i].add(o);
 }
 void clear( int pos ) {
     if( cmp==cmpb ) pos = dtot+-pos;
     for( int i=pos; i<=dtot; i+=i&-i )
         bit[i] = Info(-oo,);
 }
 Info query( int pos ) {
     if( cmp==cmpb ) pos = dtot+-pos;
     Info o(-oo,);
     for( int i=pos; i; i-=i&-i )
         o.add(bit[i]);
     return o;
 }
 void cdq( Info dp[], int lf, int rg ) {
     if( lf==rg ) {
         dp[lf].add( Info(,) );
         return;
     }
     int mid=(lf+rg)>>;
     cdq( dp, lf, mid );
     for( int i=lf; i<=rg; i++ )
         q[i] = i;
     sort( q+lf, q+rg+, cmp );
     for( int t=lf; t<=rg; t++ ) {
         int i=q[t];
         if( i<=mid ) {
             modify( pts[i].y, dp[i] );
         } else {
             Info o = query(pts[i].y);
             o.v++;
             dp[i].add( o );
         }
     }
     for( int t=lf; t<=rg; t++ ) {
         int i=q[t];
         if( i<=mid )
             clear( pts[i].y );
     }
     cdq( dp, mid+, rg );
 }
 int main() {
     scanf( "%d", &n );
     for( int i=,x,y; i<=n; i++ ) {
         scanf( "%d%d", &x, &y );
         pts[i] = Point(x,y);
         disc[++dtot] = y;
     }
     reverse( pts+, pts++n );
     sort( disc+, disc++dtot );
     dtot = unique( disc+, disc++dtot ) - disc - ;
     for( int i=; i<=n; i++ )
         pts[i].y = lower_bound( disc+, disc++dtot, pts[i].y ) - disc;

     cmp = cmpa;
     cdq( dp[], , n );
     cmp = cmpb;
     reverse( pts+, pts++n );
     cdq( dp[], , n );
     reverse( dp[]+, dp[]++n );

     Info info(-oo,);
     for( int i=; i<=n; i++ )
         info.add( dp[][i] );
     printf( "%d\n", info.v );
     for( int i=; i<=n; i++ ) {
         if( dp[][i].v+dp[][i].v- == info.v ) {
             ans[i] = dp[][i].c*dp[][i].c/info.c;
         } else
             ans[i] = 0.0;
     }
     reverse( ans+, ans++n );
     for( int i=; i<=n; i++ )
         printf( "%.5Lf\n", ans[i] );
 }