HDOJ 1824 - Let's go home 简单构图2-set

来源：互联网发布：java linux 时间戳编辑：程序博客网时间：2024/06/05 12:03

一个队看作一个组.. 队长看成一个点..两个队员一起看作一个点...构造典型的2-sat模型...用tarjan判断可行性...

在tarjan里弹栈过程中忘记把instack置为false了...WA了好久..细心...

Program:

#include<iostream>#include<stdio.h>#include<string.h>#include<cmath>#include<queue>#include<stack>#include<set>#include<algorithm>#define ll long long#define oo 10007#define pi acos(-1.0)#define MAXN 3005using namespace std; struct node{       int x,y,next;}line[10005]; int n,id[MAXN],dfn[MAXN],_next[MAXN],low[MAXN],tp[MAXN],_DfsIndex,tpnum;bool instack[MAXN];stack<int> mystack;void addline(int x,int y,int m){       line[m].next=_next[x],_next[x]=m;       line[m].x=x,line[m].y=y;}void tarjan(int x){       int k,y;       dfn[x]=low[x]=++_DfsIndex;       mystack.push(x);       instack[x]=true;       for (k=_next[x];k;k=line[k].next)       {              y=line[k].y;              if (!dfn[y])              {                      tarjan(y);                      low[x]=min(low[x],low[y]);              }else               if (instack[y])                       low[x]=min(low[x],dfn[y]);       }       if (dfn[x]==low[x])       {              tpnum++;              do              {                      x=mystack.top();                      mystack.pop();                      instack[x]=false;                      tp[x]=tpnum;              }while (dfn[x]!=low[x]);       }       return;}bool judge(){       int i;       for (i=0;i<n;i++)           if (tp[i<<1]==tp[(i<<1)|1]) return false;       return true;}int main(){           int i,m;        while (~scanf("%d%d",&n,&m))       {                 for (i=0;i<n;i++)               {                        int c,a,b;                        scanf("%d%d%d",&c,&a,&b);                        id[c]=i<<1;                        id[a]=id[b]=(i<<1)|1;               }                 memset(_next,0,sizeof(_next));               for (i=0;i<m;i++)               {                        int x,y;                        scanf("%d%d",&x,&y);                        addline(id[x],id[y]^1,i<<1);                        addline(id[y],id[x]^1,(i<<1)|1);               }                 memset(dfn,0,sizeof(dfn));               memset(instack,false,sizeof(instack));               while (!mystack.empty()) mystack.pop();                _DfsIndex=tpnum=0;                for (i=0;i<(n<<1);i++)                   if (!dfn[i]) tarjan(i);               if (judge()) printf("yes\n");                      else  printf("no\n");                      }       return 0;}