SUOI07 区间平均++ (二分答案+前缀和)

 1 #include<bits/stdc++.h>
 2 #define pa pair<int,int>
 3 #define ll long long
 4 using namespace std;
 5 const int maxn=1e6+5;
 6 
 7 inline ll rd(){
 8     ll x=0;char c=getchar();int neg=1;
 9     while(c<‘0‘||c>‘9‘){if(c==‘-‘) neg=-1;c=getchar();}
10     while(c>=‘0‘&&c<=‘9‘) x=x*10+c-‘0‘,c=getchar();
11     return x*neg;
12 }
13 
14 int N,K,Ma,Mi,num[maxn];
15 double sum[maxn];
16 
17 inline bool judge(int &x,int &y,double r){
18     int a=-1,b=N+1;
19     for(int i=1;i<=N;i++) sum[i]=sum[i-1]+num[i]-r;
20     double mi=1e9;int mn;bool re=0;
21     for(int i=K;i<=N;i++){
22         if(mi>=sum[i-K]) mi=sum[i-K],mn=i-K;
23         if(sum[i]>=mi){
24             re=1;if(b-a>i-mn||(b-a==i-mn&&mn<a)) a=mn,b=i;
25         }
26     }if(re) x=a+1,y=b;
27     return re;
28 }
29 
30 int main(){
31     int i,j,k;
32     N=rd();K=rd();Ma=-10000;Mi=10000;
33     for(i=1;i<=N;i++) num[i]=rd(),Ma=max(num[i],Ma),Mi=min(num[i],Mi);
34     double l=Mi-1,r=Ma+1;int a,b;
35     while(l<=r-1e-7){
36         double m=(l+r)/2;
37         if(judge(a,b,m)) l=m+1e-6;
38         else r=m-1e-6;
39     }printf("%d %d %.4f",a,b,l);
40     return 0;
41 }