OIFC20241113

考试总结

不嘻嘻

心态裂开了

挂挂挂

T1

简单期望，可以对 $2n$ 个数排序，然后算每个数的期望排名乘上权值，遇到冲突的数就暂时剔除冲突那个概率算完加回去就好了

傻逼出题人卡常，上个快读才过

#include<bits/stdc++.h>
#define int long long
using namespace std;
const int N=1e7+5;
const int mod=1e9+7;
int read(){
    int a=0,s=0,c=getchar();
    while(!isdigit(c)) s|=(c=='-'),c=getchar();
    while(isdigit(c)) a=a*10+c-48,c=getchar();
    return a;
}
struct node{
    int val;
    int p;
    int id;
}w[N];
bool cmp(node x,node y){
    return x.val<y.val;
}
int n;
int cut[N];
signed main(){
    freopen("good.in","r",stdin);
    freopen("good.out","w",stdout);
    n=read();
    for(int i=1;i<=n;i++){
        w[i*2-1].val=read();
        w[i*2].val=read();
        w[i*2-1].p=read();
        w[i*2].p=read();
        w[i*2-1].id=w[i*2].id=i;
    }
    sort(w+1,w+2*n+1,cmp);
    int P=0;
    int ans=0;
    for(int i=1;i<=2*n;i++){        
        ans=(ans+((((P+1-cut[w[i].id]+mod)%mod+mod)%mod)*w[i].p%mod)*w[i].val)%mod;
        cut[w[i].id]=w[i].p;
        P+=w[i].p,P%=mod;
        // cout<<P<<endl;
    }
    cout<<ans;
}