【HDOJ6606】Distribution of books（二分，BIT）

题意：给定一个长为n的数组，要求挑它前缀的一段，将其分成k段，使得每段和的最大值最小

1<=k<=n<=2e5，abs(a[i])<=1e9

思路：

刚开始写了线段树TLE

改维护后缀的BIT也TLE

暴力sort改归并排序才卡过去

怀疑用map离散化不靠谱

 #include<bits/stdc++.h>
 using namespace std;
 typedef long long ll;
 typedef unsigned int uint;
 typedef unsigned long long ull;
 typedef pair<int,int> PII;
 typedef pair<ll,ll> Pll;
 typedef vector<int> VI;
 typedef vector<PII> VII;
 typedef pair<ll,ll>P;
 #define N  400010
 #define M  200010
 #define fi first
 #define se second
 #define MP make_pair
 #define pi acos(-1)
 #define mem(a,b) memset(a,b,sizeof(a))
 #define rep(i,a,b) for(int i=(int)a;i<=(int)b;i++)
 #define per(i,a,b) for(int i=(int)a;i>=(int)b;i--)
 #define lowbit(x) x&(-x)
 #define Rand (rand()*(1<<16)+rand())
 #define id(x) ((x)<=B?(x):m-n/(x)+1)
 #define ls p<<1
 #define rs p<<1|1

 const ll MOD=1e9+,inv2=(MOD+)/;
       double eps=1e-;
       ll INF=1e10;
       ll inf=5e13;
       int dx[]={-,,,};
       int dy[]={,,-,};

 map<ll,int> mp;
 int t[N],n,k,id;
 ll s[M],a[M],b[M],c[N];

 int read()
 {
    int v=,f=;
    char c=getchar();
    while(c<||<c) {if(c=='-') f=-; c=getchar();}
    while(<=c&&c<=) v=(v<<)+v+v+c-,c=getchar();
    return v*f;
 }

 void update(int x,int y)
 {
     while(x)
     {
         t[x]=max(t[x],y);
         x-=lowbit(x);
     }
 }

 int query(int x)
 {
     int res=-2e6;
     while(x<=id)
     {
         res=max(res,t[x]);
         x+=lowbit(x);
     }
     return res;
 }

 int isok(ll mid)
 {
     mp.clear();
     int m=;
     rep(i,,n+) b[i]=a[i]-mid;
     int i=,j=;
     while(i<=n+&&j<=n+)
     {
         m++;
         if(a[i]<b[j])
         {
             c[m]=a[i];
             i++;
         }
          else
          {
              c[m]=b[j];
              j++;
          }
     }
     while(i<=n+)
     {
         c[++m]=a[i];
         i++;
     }
     while(j<=n+)
     {
         c[++m]=b[j];
         j++;
     }
     id=;
     mp[c[]]=;
     rep(i,,m)
      if(c[i]!=c[i-]) mp[c[i]]=++id;
     rep(i,,id) t[i]=-2e6;
     update(mp[],);
     int ans=,flag=;
     rep(i,,n)
     {
         int tmp=query(mp[s[i]-mid]);
         ans=max(ans,tmp+);
         if(ans>=k) return ;
         update(mp[s[i]],tmp+);
     }
     return ;
 }

 int main()
 {
     int cas=read();
     while(cas--)
     {
         n=read(),k=read();
         s[]=;
         rep(i,,n)
         {
             int x=read();
             s[i]=s[i-]+x;
         }
         rep(i,,n+) a[i]=s[i-];
         sort(a+,a+n++);
         ll l=-1e10,r=1e10,last=1e10;
         while(l<=r)
         {
             ll mid=(l+r)>>;
             if(isok(mid)){last=mid; r=mid-;}
              else l=mid+;
         }
         printf("%I64d\n",last);
     }

     return ;
 }