4518: [Sdoi2016]征途|斜率优化

Posted 2022-12-15 ws_yzy

裸的斜率优化。。我考场上SB写暴力

#include<algorithm>
#include<iostream>
#include<complex>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<vector>
#include<cmath>
#include<queue>
#include<ctime>
#include<set>
#include<map>
#define N 3333
#define inf 1e9
using namespace std;
long long sum[N],a[N],b[N],*f=a,*g=b;
int q[N],n,m;
double slop(int x,int y)

    return double(g[x]-g[y]+sum[x]*sum[x]-sum[y]*sum[y])/(sum[x]-sum[y]);

int main()

    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++)
        scanf("%d",&sum[i]),sum[i]+=sum[i-1];
    for(int i=1;i<=n;i++) f[i]=sum[i]*sum[i];
    for(int o=1;o<m;o++)
    
        int l=1,r=1; swap(f,g);q[1]=0;
        for(int i=1;i<=n;i++)
        
            while(l<r&&slop(q[l],q[l+1])<2*sum[i])l++;
            f[i]=g[q[l]]+(sum[i]-sum[q[l]])*(sum[i]-sum[q[l]]);
            while(l<r&&slop(q[r],q[r-1])>slop(q[r],i))r--;
            q[++r]=i;
        
    
    cout<<m*f[n]-sum[n]*sum[n];