bzoj 2832

Posted 2020-12-02 yinwuxiao

题解

代码：

#include <bits/stdc++.h>
#define ll long long
using namespace std;
const ll N=500;
ll total,f,n,ans;
struct re{
  ll a,b;
}a[N];
bool cmp(re x,re y)
{
  return(x.a<y.a);
}
double Random() { return rand()/(double) RAND_MAX ;}
/*ll judge(ll x)
{
  if (x<=0) return 0;
  ll xx=total-f*x,day=0,res=0;
  for (ll i=1;i<=n;i++)
  {
    if (log2(x)+log2(a[i].a)>log2(xx))
    {
      res+=xx/a[i].a;
      break;
    }
    ll num=min(xx/a[i].a/x,a[i].b-day+1);
    day+=num; xx-=num*a[i].a*x;
    res+=num*x;
  }
  ans=max(ans,res);
  return(res);
}*/
ll judge(ll times)
{
        if(times<=0) return 0;
        ll Money = total - times * f;
        ll res = 0, num, day = 0;
        for(int i=1;i<=n;i++)
        {
            num = min(Money / a[i].a / times, a[i].b - day + 1);
            Money -= num * a[i].a * times;
            day += num; res += times * num;
            if(day <= a[i].b)
            {
                num = Money / a[i].a;
                res += num;
                ans = max(ans, res);
                return res;
            }
        }
        ans = max(ans, res);
        return res;
}
void sa(double T)
{
  ll now=1;
  while (T>=1)
  {
    ll a=now+(ll)(T*(Random()*2-1));
    if (a<=0) a=T*Random();
    ll de=judge(a)-judge(now);
    if (de>0) now=a;
    T*=0.97;
  }
}
/*void sa(double T)
{
        ll Now = 1;
        while(T >= 1)
        {
            ll A = Now + (ll)(T * (Random()*2-1)) ;
            if(A<=0) A = T*Random();
            ll dE = judge(A) - judge(Now);
            if(dE > 0)
                Now = A;
            T *= 0.97;
        }
         
}*/
int main()
{
  srand(time(0)^size_t(new char));
  freopen("1.in","r",stdin);
  freopen("1.out","w",stdout);
  ios::sync_with_stdio(false);
  while (cin>>total>>f>>n)
  {
    ans=0;
    for(ll i=1;i<=n;i++)
      cin>>a[i].a>>a[i].b;
    sort(a+1,a+n+1,cmp);
    ll m=n,d=-1;
    n=0;
    for (ll i=1;i<=m;i++)
      if (a[i].b>d) a[++n]=a[i],d=a[i].b;
    sa(total/f+1);
    cout<<ans<<endl;
  }
  return 0;
}