HDU4258+DP+斜率优化

对于斜率优化的dp还不是很懂。。。。。。。。。

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 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 }