HDU4258+DP+斜率优化

对于斜率优化的dp还不是很懂。。。。。。。。。

View Code 
 1 /*
 2 dp+斜率优化
 3 */
 4 #include<stdio.h>
 5 #include<string.h>
 6 #include<stdlib.h>
 7 #include<algorithm>
 8 #include<iostream>
 9 #include<queue>
10 #include<math.h>
11 using namespace std;
12 const int maxn = 1000005;
13 const int cl = 0x7F;
14 typedef __int64 int64;
15 int64 a[ maxn ],dp[ maxn ];
16 int que[ maxn ];
17 double get( int64 x,int64 y ){
18     return 1.0*( dp[x]-dp[y]+a[x+1]*a[x+1]-a[y+1]*a[y+1] )/( 2.0*(a[x+1]-a[y+1]) );
19 }
20 void dp_solve( int64 n,int64 c ){
21     memset( dp,cl,sizeof( dp ) );
22     dp[ 0 ] = 0;
23     int head,tail;
24     head = tail = 1;
25     que[ 1 ] = 0;
26     for( int i=1;i<=n;i++ ){
27          while( head<tail&&get( que[ head+1 ],que[ head ] )<=(double)a[ i ]  )
28              head++;
29          dp[ i ] = dp[ que[head] ]+c+( a[i]-a[ que[head]+1 ])*( a[i]-a[ que[head]+1 ] );
30          while( head<tail&&get( i,que[ tail ] )<=get( que[ tail ],que[ tail-1 ] ) )
31              tail--;
32          que[ ++tail ] = i;
33     }
34     printf("%I64d\n",dp[ n ]);
35     return ;
36 }
37 int main(){
38     int64 n,c;
39     while( scanf("%I64d%I64d",&n,&c)==2 ){
40         if( n==0 && c==0 ) break;
41         for( int i=1;i<=n;i++ )
42             scanf("%I64d",&a[ i ]);
43         dp_solve( n,c );
44     }
45     return 0;
46 }

 

posted @ 2013-04-03 21:33  xxx0624  阅读(270)  评论(0)  编辑  收藏  举报