POJ3648 Wedding 【2-SAT】

题意：新娘新郎和每对夫妇，都分开坐，新娘不希望看到对面有特殊关系的一对人

思路：可以考虑选一些人坐在新娘对面（也就是新郎这一边），新郎必须选（建边 新娘->新郎），有特殊关系的每一对人建边，反着输出新娘这一边的人

#include<stdio.h>#include<iostream>#include<string.h>#include<string>#include<stdlib.h>#include<math.h>#include<vector>#include<list>#include<map>#include<stack>#include<queue>#include<algorithm>#include<numeric>#include<functional>using namespace std;typedef long long ll;const int maxn = 1005;struct edge{int to,next;bool cut;}ed[maxn];int head[maxn], tot;  int Low[maxn], DFN[maxn], Stack[maxn];  int Index, top;bool Instack[maxn]; int block,belong[maxn];  int bridge;void init(){memset(head, -1, sizeof(head));      memset(DFN, 0, sizeof(DFN));       memset(Instack, false, sizeof(Instack));       block = tot = 0;    Index = top = 0;    bridge = 0; }void Tarjan(int u,int pre){    int v;    Low[u] = DFN[u] = ++Index;    Stack[top++] = u;    Instack[u] = true;    for(int i = head[u];i != -1;i = ed[i].next)    {        v = ed[i].to;        //if(v == pre)continue; //无向无重边 用，只要不往回走         //if(ed[i].id == pre) continue; //无向图重边判定，不走同一条边         if( !DFN[v] )        {            Tarjan(v,u);            //Tarjan(v,ed[i].id); //无向图重边判定            if( Low[u] > Low[v] )Low[u] = Low[v];            if(Low[v] > DFN[u])            {                bridge++;                ed[i].cut = true;                ed[i^1].cut = true;            }        }        else if( Instack[v] && Low[u] > DFN[v] )            Low[u] = DFN[v];    }    if(Low[u] == DFN[u])    {        block++;        do        {            v = Stack[--top];            Instack[v] = false;            belong[v] = block;        }        while( v!=u );    }}//使无向图双连通，（叶子+1） / 2void add(int x,int y){ed[tot].to = y;ed[tot].next = head[x];ed[tot].cut = 0;//ed[tot].id = num; //无向图重边判定 head[x] = tot++;}void SCC(int n)  {      for(int i = 0; i < n; i++)          if(!DFN[i])             Tarjan(i,-1);  }int bian(int a,char c,int n){if(c == 'w')return a;elsereturn a+n;}int fan(int a,char c,int n){if(c == 'w')return a+n;elsereturn a;}int main(void){int n,m,a,b;char c,d;while(scanf("%d%d",&n,&m)!=EOF && n+m){init();add(0,n);while(m--){scanf("%d%c%d%c",&a,&c,&b,&d);add(bian(a,c,n),fan(b,d,n));add(bian(b,d,n),fan(a,c,n));}SCC(2*n);int flag = 1;for(int i = 1; i < n; i++){if(belong[i] == belong[i+n]){flag = 0;break;}}if(!flag){printf("bad luck\n");continue;}for(int i = 1; i < n; i++){if(belong[i] > belong[i+n])printf("%dw%c",i,i==n-1?'\n':' ');elseprintf("%dh%c",i,i==n-1?'\n':' ');}}return 0;}