"Dp+ tree-like array" bzoj1264-[ahoi2006 "gene matches match

"The main topic"

Given the number of N and two sequences with a length of n*5, the number in the two series is 1. n composition, and 1. Each number in n occurs exactly 5 times, and an LCS of two sequences is obtained.

Ideas

Preprocess the five locations that each number appears in A[i]. F[i] shows the longest common substring at the end of A[i] (* This avoids the discussion of intersections).

Processing B[i] In turn, for each b[i] found in a[i] Five position transfer, with the NOWP, the transfer is very simple: F[nowp]=max (f[nowp],query (nowp-1) +1), where the prefix maximum value needs to be maintained.

To know that the prefix maximum value can be maintained with bit.

It is important to note, however, that it must be from 5 Downto 1. Why is it? Since the NOWP is arranged in ascending order, if from the smallest start, then the subsequent F-transfer may be calculated in the previously obtained F, but in fact they correspond to the same b[i].

So from the big to the small.

1#include <iostream>2#include <cstdio>3#include <cstring>4#include <algorithm>5#include <cmath>6 using namespacestd;7 Const intmaxn=20000+ -;8 intN;9 inta[5*maxn],b[5*maxn],e[5*maxn],f[5*MAXN];Ten //F[i] represents the longest common substring at the end of A[i], so you can avoid discussing cross - One intpos[maxn][6]; A intans=0; -  - intLowbit (intx) the { -     return(x& (-x)); - } -  + intQueryintx) - { +     intret=0;//the initial value must be set to 0 instead of-1 . A      while(x>0) Ret=max (Ret,e[x]), x-=lowbit (x); at     returnret; - } -  - voidUpdateintXintDelta) - { -      while(x<=5*n) E[x]=max (E[x],delta), x+=lowbit (x); in }  -  to voidInit () + { -Memset (E,0,sizeof(e)); theMemset (F,0,sizeof(f)); *Memset (A,0,sizeof(a)); $scanf"%d",&n);Panax Notoginseng      for(intI=1; i<=5*n;i++)  -     { thescanf"%d",&a[i]); +pos[a[i]][++pos[a[i]][0]]=i; A     } the      for(intI=1; i<=5*n;i++) scanf ("%d",&B[i]);  + } -  $ voidDP () $ { -      for(intI=1; i<=5*n;i++) -          for(intj=5; j>=1; j--)//we must move from the back . the         { -             intnowp=Pos[b[i]][j];WuyiF[nowp]=max (F[nowp],query (nowp-1)+1); the Update (NOWP,F[NOWP]); -ans=Max (ANS,F[NOWP]); Wu         } -printf"%d\n", ans); About } $  - intMain () - { - init (); A DP (); +     return 0;  the}

"Dp+ tree-like array" bzoj1264-[ahoi2006 "gene matches match