HDU4115. Eliminate the Conflict (scissors stone cloth)--2-sat feasibility judgment

http://acm.hdu.edu.cn/showproblem.php?pid=4115

Title Description:
Bob, and Alice two in the N-round scissors-stone cloth, known Bob N-wheel out of the case, for Alice given the M-group limit, as long as each round Alice did not lose, after the N-round even if Alice wins. Judging if she can win.

Analysis:
For the first round of Bob's case, Alice has two options (equivalent to the I variable has two states), and then we just deal with contradictory edges

//62ms 2156K 3312 B#include <cstring>#include <cstdio>#include <queue>#include <vector>#include <iostream>Const intmaxn=20010;Const intmaxm=40010;using namespace STD;intLow[maxn],dfn[maxn],sccno[maxn],scc,dfs_clock,top;intSTACK[MAXN];BOOLINSTACK[MAXN];structEdge {intTo,next;} edge[maxm<<1];intHead[maxn],tot;voidAddedge (intUintV) {edge[tot].to=v;edge[tot].next=head[u];head[u]=tot++;}voidInit () {tot=0;memset(Head,0xFF,sizeof(head));}voidDfsintu) {intV    Low[u]=dfn[u]=++dfs_clock; instack[u]=1; Stack[top++]=u; for(intI=head[u]; i!=-1; I=edge[i].next) {v=edge[i].to;if(!dfn[v]) {DFS (v);if(Low[u]>low[v]) low[u]=low[v]; }Else if(Instack[v]&&low[u]>dfn[v]) low[u]=dfn[v]; }if(Low[u]==dfn[u]) {scc++; for(;;)            {V=stack[--top]; instack[v]=0; SCCNO[V]=SCC;if(V==u) Break; }    }}BOOLSolveable (intN) {memset(DFN,0,sizeof(DFN));memset(Instack,false,sizeof(Instack)); Dfs_clock=top=scc=0; for(intI=0; i<n; ++i) {if(!dfn[i]) DFS (i); } for(intI=0; i<n; i+=2) {if(sccno[i]==sccno[i^1])return false; }return true;}intMain () {#ifndef Online_judgeFreopen ("In.txt","R", stdin);#endif //Online_judge     intt,n,m,u,v,c,cas=1;inta[maxn],b[maxn][2];scanf("%d", &t); while(t--) {scanf("%d%d", &n,&m); for(intI=0; i<n;++i) {scanf("%d", &a[i]);if(a[i]==1) {b[i][0]=1; b[i][1]=2; }if(a[i]==2) {b[i][0]=2; b[i][1]=3; }if(a[i]==3) {b[i][0]=3; b[i][1]=1; }} init (); while(m--) {scanf("%d%d%d", &u,&v,&c); U--, v--;if(c==0){if(b[u][0]!=b[v][0]) {Addedge (u<<1,v<<1|1); Addedge (v<<1,u<<1|1); }if(b[u][0]!=b[v][1]) {Addedge (u<<1,v<<1); Addedge (v<<1|1,u<<1|1); }if(b[u][1]!=b[v][0]) {Addedge (u<<1|1,v<<1|1); Addedge (v<<1,u<<1); }if(b[u][1]!=b[v][1]) {Addedge (u<<1|1,v<<1); Addedge (v<<1|1,u<<1); }            }Else{if(b[u][0]==b[v][0]) {Addedge (u<<1,v<<1|1); Addedge (v<<1,u<<1|1); }if(b[u][0]==b[v][1]) {Addedge (u<<1,v<<1); Addedge (v<<1|1,u<<1|1); }if(b[u][1]==b[v][0]) {Addedge (u<<1|1,v<<1|1); Addedge (v<<1,u<<1); }if(b[u][1]==b[v][1]) {Addedge (u<<1|1,v<<1); Addedge (v<<1|1,u<<1); }            }        }printf("Case #%d:", cas++);if(Solveable (n<<1))puts("Yes");Else puts("No"); }return 0;}

HDU4115. Eliminate the Conflict (scissors stone cloth)--2-sat feasibility judgment