山东省第八届acm省赛E题 三分+二分

#include<iostream>#include<cstdio>#include<cstring>#include<algorithm>using namespace std;const double eps=2*1e-8;int a[5005],b[5005],k,n,m;double res[5005],ans,f[1000005];inline bool cmp(double a,double b){    return a>b;}inline bool check(double kp,int c){    for(int i=0;i<n;i++)        res[i]=(a[i]+c)%m-kp*b[i];    sort(res,res+n,cmp);    double ans=0.0;    for(int i=0;i<k;i++)        ans+=res[i];    if(ans>=0)        return true;    else        return false;}inline double cal(int k){    if(f[k]>0)        return f[k];    double l=0.0,r=m,mid;    int cnt=0;    while(r-l>eps)    {        cnt++;        mid=(r+l)/2;        if(check(mid,k))            l=mid;        else            r=mid;    }    return f[k]=mid;}int main(){    while(scanf("%d%d%d",&n,&k,&m)!=EOF)    {        memset(f,0,sizeof(f));        for(int i=0;i<n;i++)            scanf("%d",a+i);        for(int i=0;i<n;i++)            scanf("%d",b+i);        ans=0.0;        int sl=0,sr=m-1,ll,rr;        while(sl+1<sr)        {            int rr=(sl+2*sr)/3.0+0.5,ll=(sl*2+sr)/3.0+0.5;            if(cal(ll)>cal(rr))                sr=rr;            else                sl=ll;        }        printf("%.7f\n",max(f[sr],f[sl]));    }    return 0;}