P2985 [USACO10FEB]喫巧克力

題目傳送

二分答案+貪心

需要注意的問題是，最後上下的巧克力要在最後一天喫完！
因爲這個問題，調了2個小時！

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath> 
#define LL long long
using namespace std;
int n,d,a[50009],eat[50009],t[50009];
LL s[50009];
bool check(LL x)
{
//  memset(eat,0,sizeof(eat));
    LL sum=0,last=0;
    int j=1,day=1;
    while(day<=d&&(j<=n||last>=x))
    {
        LL need=x-last;
        if(need>0)
        {
            while(s[j]<sum+need&&j<=n)
            {
                eat[j]=day;
                j++;
            }
            if(s[j]<sum+need) return 0;
            eat[j]=day;
            last=(last+s[j]-sum)/2;
            sum=s[j];
            j++;
            day++;
        }
        else day++,last/=2;
    }
    if(day<=d) return 0;
    for(int i=1;i<=j-1;i++) t[i]=eat[i];
    for(int i=j;i<=n;i++) t[i]=d;
    return 1;
}
int main()
{
    //freopen("a.txt","r",stdin);
    //freopen("b.txt","w",stdout);
    scanf("%d%d",&n,&d);
    for(int i=1;i<=n;i++)
    {
        scanf("%d",&a[i]);
        s[i]=s[i-1]+1ll*a[i];
    }

    LL L=0,R=5e10+7,mid,ans=L;
    while(L<=R)
    {
        mid=(L+R)>>1;
        if(check(mid)) ans=mid,L=mid+1;
        else R=mid-1;
    } 
    printf("%lld\n",ans);
    for(int i=1;i<=n;i++)
     printf("%d\n",t[i]);
    return 0;
}