问题：
printf("%.5f ",0):为什么错了？
注意：
初始值很重要
题解：
三维偏序问题；
记录从前往后最长上升子序列长度pref，条数preg
从后往前suff，sufg
如果对于某个点pref+suff==ans-1，那么打掉它的概率 preg*sufg/tot
Wa了好多次QWQ
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define lowbit(x) x&(-x)
using namespace std;
typedef long long Lint;
const int maxn=3000009; int n;
int ans; double tot;
int pref[maxn];
double preg[maxn];
int suff[maxn];
double sufg[maxn]; struct Missile{
int x,z,y,f;
double g;
}a[maxn]; int b[maxn],nn; int c[maxn];
double d[maxn];
int add(int x,int val,double q){
while(x<=nn){
if(val>c[x]){
c[x]=val;
d[x]=q;
}else if(val==c[x]){
d[x]+=q;
}
x+=lowbit(x);
}
}
int refresh(int x){
while(x<=nn){
c[x]=d[x]=0;
x+=lowbit(x);
}
}
int querymax(int x){
int ret=0;
while(x){
ret=max(ret,c[x]);
x-=lowbit(x);
}
return ret;
}
double querysum(int x,int val){
double ret=0;
while(x){
if(c[x]==val){
ret+=d[x];
}
x-=lowbit(x);
}
return ret;
} int cmpx(const Missile &tmp1,const Missile &tmp2){
return tmp1.x<tmp2.x;
}
int cmpy(const Missile &tmp1,const Missile &tmp2){
if(tmp1.y==tmp2.y)return tmp1.z<tmp2.z;
else return tmp1.y<tmp2.y;
}
int cdq(int l,int r){
if(l==r)return 0;
int mid=(l+r)>>1;
cdq(l,mid);
int t1=l,t2=mid+1;
sort(a+l,a+mid+1,cmpy);
sort(a+mid+1,a+r+1,cmpy);
while(t2<=r){
while((t1<=mid)&&(a[t1].y<=a[t2].y)){
add(a[t1].z,a[t1].f,a[t1].g);
++t1;
}
int tmp=querymax(a[t2].z)+1;
if(tmp>a[t2].f){
a[t2].f=tmp;
a[t2].g=querysum(a[t2].z,tmp-1);
}else if(tmp==a[t2].f){
a[t2].g+=querysum(a[t2].z,tmp-1);
}
++t2;
}
for(int i=l;i<=mid;++i){
refresh(a[i].z);
}
sort(a+mid+1,a+r+1,cmpx);
cdq(mid+1,r);
} int work1(){
for(int i=1;i<=n;++i){
a[i].y=-a[i].y;
a[i].z=nn-a[i].z+1;
a[i].f=a[i].g=1;
}
cdq(1,n);
for(int i=1;i<=n;++i){
ans=max(ans,a[i].f);
pref[a[i].x]=a[i].f;
preg[a[i].x]=a[i].g;
}
for(int i=1;i<=n;++i){
if(a[i].f==ans)tot=tot+a[i].g;
}
}
int work2(){
for(int i=1;i<=n;++i){
a[i].x=-a[i].x;
a[i].y=-a[i].y;
a[i].z=nn-a[i].z+1;
a[i].f=a[i].g=1;
}
sort(a+1,a+1+n,cmpx);
cdq(1,n);
for(int i=1;i<=n;++i){
suff[-a[i].x]=a[i].f;
sufg[-a[i].x]=a[i].g;
}
}
int Getans(){
printf("%d\n",ans);
for(int i=1;i<=n;++i){
if(pref[i]+suff[i]-1==ans){
printf("%.5f ",preg[i]*sufg[i]/tot);
}else{
printf("%d ",0);
}
}
} int minit(){
tot=0;
ans=0;
for(int i=0;i<=n;++i){
d[i]=c[i]=0;
}
} int main(){
// freopen("Misslie.in","r",stdin);
// freopen("Misslie.out","w",stdout); scanf("%d",&n);
minit();
for(int i=1;i<=n;++i){
scanf("%d%d",&a[i].y,&a[i].z);
a[i].x=i;
b[i]=a[i].z;
}
sort(b+1,b+1+n);
nn=unique(b+1,b+1+n)-b-1;
for(int i=1;i<=n;++i){
a[i].z=lower_bound(b+1,b+1+nn,a[i].z)-b;
} work1();
work2(); Getans();
return 0;
}