BZOJ 4518: [Sdoi2016]征途

来源：互联网发布：复杂网络同步编辑：程序博客网时间：2024/04/30 11:45

http://www.lydsy.com/JudgeOnline/problem.php?id=4518

山东2016 省选题

当时写了 60分的

那时候还不会斜率优化

其实搞完之后就是很裸的斜率优化

再有就是很多细节斜率优化错起来要调半天

/**************************************************************    Problem: 4518    User: sxb_201    Language: C++    Result: Accepted    Time:804 ms    Memory:213732 kb****************************************************************/ #include <cstdio>#include <cstring>#include <iostream>#include <algorithm>using namespace std;const long long MAXN=3000+10;struct H{    long long x[MAXN];    long long y[MAXN];    long long head,tail;}; long long n,m,v[MAXN],s[MAXN],f[MAXN][MAXN];H team[MAXN];  long long get_b(long long i,long long head,long long k){    return team[i].y[head]-k*team[i].x[head];} bool can(long long i,long long a,long long b,long long cx,long long cy){    long long ax=team[i].x[a];    long long ay=team[i].y[a];    long long bx=team[i].x[b];    long long by=team[i].y[b];         long long x1=bx-ax;    long long y1=by-ay;    long long x2=cx-bx;    long long y2=cy-by;    return y1*x2-x1*y2<0;} int main(){    cin >>n >>m;    for(long long i=1;i<=n;i++) scanf("%lld",&s[i]),s[i]+=s[i-1];    for(long long i=1;i<=m;i++)    {        for(long long j=1;j<=n;j++)        {            while(team[i-1].head<team[i-1].tail && get_b(i-1,team[i-1].head,2*s[j])>=get_b(i-1,team[i-1].head+1,2*s[j])) team[i-1].head++;            f[i][j]=get_b(i-1,team[i-1].head,2*s[j])+s[j]*s[j];                         long long x=s[j],y=f[i][j]+s[j]*s[j];            while(team[i].head<team[i].tail && can(i,team[i].tail-1,team[i].tail,x,y)==false) team[i].tail--;            long long tail=++team[i].tail;            team[i].x[tail]=x;            team[i].y[tail]=y;        }    }/*  for(long long i=0;i<=team[2].tail;i++) cout<<team[2].x[i]<<' '<<team[2].y[i]<<endl;;cout<<endl;    for(long long i=1;i<=m;i++)    {        for(long long j=1;j<=n;j++)            cout<<f[i][j]<<' ';        cout<<endl;    }*/    cout<<m*f[m][n]-s[n]*s[n];    return 0;}

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