LOJ P10012 Best Cow Fences 题解

每日一题 day48 打卡

Analysis

二分答案，判断序列的平均值是否大于等于mid

具体怎么实现呢？

将序列减去mid，再用前缀和来维护平均值就好了

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #define int long long
 #define maxn 100000+10
 #define INF 2147483647
 #define rep(i,s,e) for(register int i=s;i<=e;++i)
 #define dwn(i,s,e) for(register int i=s;i>=e;--i)
 using namespace std;
 inline int read()
 {
     int x=,f=;
     char c=getchar();
     while(c<''||c>'') {if(c=='-') f=-; c=getchar();}
     while(c>=''&&c<='') {x=x*+c-''; c=getchar();}
     return f*x;
 }
 inline void write(int x)
 {
     if(x<) {putchar('-'); x=-x;}
     if(x>) write(x/);
     putchar(x%+'');
 }
 
 int n,L,l,r,ans;
 int a[maxn],sum[maxn],b[maxn];
 inline bool check(int x)
 {
     rep(i,,n) b[i]=a[i];
     rep(i,,n) b[i]-=x;
     rep(i,,n) sum[i]=sum[i-]+b[i];
     int min_val=INF;
     rep(i,L,n)
     {
         min_val=min(min_val,sum[i-L]);
         if(sum[i]-min_val>=) return true;
     }
     return false;
 }
 signed main()
 {
     n=read();L=read();
     rep(i,,n)
     {
         a[i]=read();
         a[i]*=;
     }
     l=,r=;
     while(l<r)
     {
         int mid=(l+r+)/;
         if(check(mid)==true)
         {
             ans=mid;
             l=mid;
         }
         else r=mid-;
     }
     if(ans%==) write(ans+);
     else write(ans);
     return ;
 }

请各位大佬斧正（反正我不认识斧正是什么意思）