【hdu3507】Print Article 【斜率优化dp】

题意

  https://cn.vjudge.net/problem/HDU-3507

分析

  斜率优化的模板题

  

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <algorithm>
 4 #include <iostream>
 5 
 6 using namespace std;
 7 typedef long long LL;
 8 const int maxn=500000+10;
 9 int n,m;
10 int c[maxn],sum[maxn],f[maxn],q[maxn];
11 int head,tail;
12 int Y(int j){
13     return f[j]+sum[j]*sum[j];
14 }
15 int X(int j){
16     return sum[j];
17 }
18 
19 double grand(int i,int j){
20     return (Y(i)-Y(j))/(X(i)-X(j));
21 }
22 
23 int main(){
24     while(scanf("%d%d",&n,&m)!=EOF){
25         for(int i=1;i<=n;i++){
26             scanf("%d",&c[i]);
27             sum[i]=sum[i-1]+c[i];
28         }
29         head=tail=0;
30         q[tail++]=0;
31         for(int i=1;i<=n;i++){
32             while(head+1<tail&&((Y(q[head+1])-Y(q[head]))<=2*sum[i]*(X(q[head+1])-X(q[head]))))head++;
33             f[i]=f[q[head]]+(sum[i]-sum[q[head]])*(sum[i]-sum[q[head]])+m;
34 //            printf("%d %d %d\n",i,q[head],f[i]);
35 //            printf("%d %d\n",head,tail);
36             while(head+1<tail&&((Y(q[tail-1])-Y(q[tail-2]))*(X(i)-X(q[tail-1]))>=(X(q[tail-1])-X(q[tail-2]))*(Y(i)-Y(q[tail-1]))))tail--;
37             q[tail++]=i;
38         }
39 
40         printf("%d\n",f[n]);
41     }
42 return 0;
43 }
View Code

 

posted @ 2018-11-02 09:36  蒟蒻LQL  阅读(133)  评论(0)  编辑  收藏  举报