CEOI2017 day1-Sure Bet【三分】

从大到小排序，枚举a中选几个，在b中三分。

代码

#include<cstdio>#include<cstring>#include<algorithm>#define maxn 100006using namespace std;int n;double ans,a[maxn],b[maxn];bool cmp(double x,double y){return x>y;}double find(int x,double y){    int l=1,r=n;    while(r-l>=15){        int t=(r-l+1)/3,mid1=l+t/3,mid2=r-t/3;        if(min(y,b[mid1])-mid1>min(y,b[mid2])-mid2)r=mid2;                                              else l=mid1;    }    double sum=-1e9;    for(int i=l;i<=r;i++)sum=max(sum,min(y,b[i])-i-x);    return sum;}int main(){    freopen("b.in","r",stdin);    freopen("b.out","w",stdout);    scanf("%d",&n);    for(int i=1;i<=n;i++)scanf("%lf%lf",&a[i],&b[i]);    sort(a+1,a+1+n,cmp);sort(b+1,b+1+n,cmp);    for(int i=2;i<=n;i++)b[i]+=b[i-1];    double suma=0;    for(int i=1;i<=n;i++){        suma+=a[i];        ans=max(ans,find(i,suma));    }    printf("%.4lf",ans);    return 0;}