# BZOJ1930 [Shoi2003]pacman eats peas

Source: Internet
Author: User

DP, first built diagram, F[i][j] said a eat to I point, b eat to the maximum value of J point, transfer when the transfer topological sequence of the small, if I topological sequence is less than J, then transferred to F[k][j], otherwise transferred to F[i][k], the number of graphs to be built to optimize, otherwise it will time out. The optimization method is if the i,j is connected, then if there is an edge (i,k), x[k]>x[j] and Y[k]>y[j] then (I,K) This edge is not necessary to exist. It is better to fetch (I,J) in the j,k than to fetch (I,K) directly.

Code

`1#include <cstdio>2#include <algorithm>3 #defineN 100104 using namespacestd;5 intN,i,j,rd[n],t,w,tot,id[n];6 intdp,pre[3000000],p[n],tt[3000000],z[n],id[n],tmp;7 intf[2500][2500];8 structg{9     intx, y;Ten }a[n]; One BOOLCMP (g A,g b) A { -     if(a.x==b.x) -     returna.y<b.y; the     returna.x<b.x; - } - voidLinkintXinty) - { +dp++;p re[dp]=p[x];p [x]=dp;tt[dp]=y; - } + voidDp (intXinty) A { at     inti; -I=P[x]; -      while(i) -     { -             inta=tt[i],b=y; -             if(id[a]>Id[b]) in Swap (A, b); -             if(a!=b) toF[a][b]=max (f[a][b],f[x][y]+1); +             Else -f[a][b]=Max (f[a][b],f[x][y]); theI=Pre[i]; *     } \$ }Panax Notoginseng intMain () - { thescanf"%d",&n); +      A      for(i=1; i<=n;i++) thescanf"%d%d",&a[i].x,&a[i].y); +Sort (A +1, A +1+n,cmp); -      for(i=1; i<=n;i++) \$     { \$tmp=0x37373737*2; -      for(j=i+1; j<=n;j++) -     if(i!=j) && (a[i].x<=a[j].x) && (A[I].Y&LT;=A[J].Y) && (a[j].y<tmp)) the     { -tmp=a[j].y;Wuyird[j]++; the link (i,j); -     } Wu     } -      for(i=1; i<=n;i++) About     { \$Link0, i); rd[i]++; -Link (i,n+1); rd[n+1]++; -     } -t=0; w=1; z[w]=0; A      while(t!=W) +     { thetot++; -t++; \$id[z[t]]=tot; theid[tot]=Z[t]; theI=P[z[t]]; the          while(i) the         { -rd[tt[i]]--; in             if(rd[tt[i]]==0) the             { thew++;z[w]=Tt[i]; About             } theI=Pre[i]; the         } the     } +  -      the      for(i=1; i<=tot;i++)Bayi          for(j=i;j<=tot;j++) the Dp (Id[i],id[j]); theprintf"%d\n", f[n+1][n+1]-1); -}`

BZOJ1930 [Shoi2003]pacman eats peas

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