斜率优化DP基础XVI Open Cup named after E.V. Pankratiev. GP of Ukraine.K

这个 基本上和上一个 一样。

#include <bits/stdc++.h>
const long long mod = 1e9+7;
const double ex = 1e-10;
#define inf 0x3f3f3f3f
#define iinf 0x3f3f3f3f3f3f3f3f
using namespace std;
long long dp[3011][5011];
long long sum[5011];
long long Tsum[5011];
int Q[3011][5011];
int head[3011];
int tail[3011];
double getk(int a,int b,int k) // get the slope
{
    return (1.0*dp[k][a] - 1.0*Tsum[a] + 1.0*a*sum[a] - 1.0*(1.0*dp[k][b] - 1.0*Tsum[b] + 1.0*b*sum[b])) /(1.0*a-1.0*b);
}
int main()
{
    int N,M;
    cin >> N >> M;
        memset(dp,iinf,sizeof(dp));
        memset(sum,0,sizeof(sum));
        memset(Tsum,0,sizeof(Tsum));
        int a;
        for (int i = 1;i<=N; i++){
            scanf("%d",&a);
            sum[i]  += sum[i-1]+a;
            Tsum[i] += Tsum[i-1] + a*i;
        }
        for (int i = 0;i<=M; i++)
            head[i]=2,tail[i]=1,dp[i][0] = 0;
        for (int i = 1;i<=N;i++)
            for (int j = 1 ;j<=min(i,M);j++)
            {
                while (head[j-1]>tail[j-1]+1 && sum[i]>getk(Q[j-1][tail[j-1]+1],Q[j-1][tail[j-1]],j-1)) tail[j-1]++; // Find the best shift && Drop some shift because of the increase of sum
                int kk = Q[j-1][tail[j-1]];
                dp[j][i] = dp[j-1][kk] - kk*(sum[i]-sum[kk]) + Tsum[i] - Tsum[kk];//Shift
                while (head[j]>tail[j]+1 && getk(i,Q[j][head[j]-1],j)<getk(Q[j][head[j]-1],Q[j][head[j]-2],j)) head[j]--;//Insert the shift i && Maintain the increase of the slope
                Q[j][head[j]++] = i;//Insert i
            }
    cout << dp[M][N] <<endl;
    return 0;
}