[2-sat] HDOJ1824 let ' s go home

A brief test instructions of the problem

and hdoj 30,621 samples

Here each member has the choice and does not choose two kinds, namely the last article said $x$ and $x ' $

Map: Captain (a) left or the remaining two players (b, c) remain

So that is $ A ' \rightarrow b$, $a ' \rightarrow C $ (captain not in B must be in, captain not in C must be in)

As well as $b ' \rightarrow a$, $c ' \rightarrow a$ (b not in captain must be in, C not captain must be in)

Each pair of players, if player a leaves, then player B must go home to rest, or b leave, a home

So that's $ A \rightarrow B ' $ (a in then B must be absent) as well as $B \rightarrow a ' $ (b in then a must not)

1#include <bits/stdc++.h>2 using namespacestd;3typedefLong LongLL;4typedef pair<int,int>PI;5 #defineINF 0x3f3f3f3f6 7 Const intn=3005*2;8 Const intm=n*N;9 //Note that n is the size after the split, i.e. n <<= 1 n is the number of points (note to double) m is the i&1=0 for I true i&1=1 for I falseTen structEdge One { A     intto, NEX; - }edge[m]; - //Note N M to modify the intHead[n], edgenum; - voidAddedge (intUintv) - { -Edge e={V, head[u]}; +edge[edgenum]=E; -head[u]=edgenum++; + } A  at BOOLMark[n]; - intStack[n], top; - voidInit () - { -Memset (Head,-1,sizeof(head)); -edgenum=0; inmemset (Mark,0,sizeof(Mark)); - } to  + BOOLDfsintx) - { the     if(mark[x^1]) *         return false;//must be the point of the break first Judge $     if(Mark[x])Panax Notoginseng         return true; -mark[x]=true; thestack[top++]=x; +      for(inti=head[x];i!=-1; i=Edge[i].nex) A         if(!DFS (edge[i].to)) the             return false; +  -     return true; $ } $  - BOOLSolveintN) - { the      for(intI=0; i<n;i+=2) -         if(!mark[i] &&!mark[i^1])Wuyi         { thetop=0; -             if(!DFS (i)) Wu             { -                  while(top) Aboutmark[stack[--top]]=false; $                 if(!dfs (i^1)) -                     return false; -             } -         } A     return true; + } the  - intMain () $ { the     intN, M; the      while(~SCANF ("%d%d", &n, &m)) the     { the         intnn=n*3; - init (); in          while(n--) the         { the             intA, B, C; Aboutscanf"%d%d%d", &a, &b, &c); theAddedge (A *2+1, b*2); theAddedge (A *2+1, c*2); theAddedge (b*2+1, A *2); +Addedge (c*2+1, A *2); -         } the          while(m--)Bayi         { the             intx, y; thescanf"%d%d", &x, &y); -Addedge (x*2, y*2+1); -Addedge (y*2, x*2+1); the         } theSolve (NN)? Puts"Yes"): Puts ("No"); the     } the     return 0; -}

hdoj 1824

[2-sat] HDOJ1824 let ' s go home