《拓扑排序》hdoj 1811 拓扑排序 并查集

 #include"stdio.h"
 #include"string.h"
 #include"stdlib.h"
 #include"queue"
 using namespace std;
 #define N 10011
 #define M 20011

 int n,m;
 int father[N],indegree[N],ans;
 struct Eage{
     int from,to,next;
 }eage[M];
 int tot,head[N];
 void add(int a,int b){
     eage[tot].from=a;eage[tot].to=b;eage[tot].next=head[a];head[a]=tot++;
 }

 int find(int k)
 {
     if(father[k]==k)    return k;
     father[k]=find(father[k]);
     return father[k];
 }
 void get_map()
 {
     int i;
     int a[M],b[M];
     char str[M][3];
     int f1,f2;
     for(i=0;i<n;i++) father[i]=i;
     for(i=0;i<m;i++)
     {
         scanf("%d%s%d",&a[i],str[i],&b[i]);
         if(str[i][0]=='=')
         {
             f1=find(a[i]);
             f2=find(b[i]);
             father[f2]=f1;
         }
     }
     for(i=0;i<n;i++) f1=find(i);                 //如果想直接用某个点的father的话，这个不能漏掉。
     tot=0;
     memset(head,-1,sizeof(head));
     memset(indegree,0,sizeof(indegree));
     for(i=0;i<m;i++)
     {
         if(father[a[i]]==father[b[i]] && str[i][0]!='=')    {ans=1;break;}
         if(str[i][0]=='>')       {add(father[a[i]],father[b[i]]);indegree[father[b[i]]]++;}
         else if(str[i][0]=='<')  {add(father[b[i]],father[a[i]]);indegree[father[a[i]]]++;}
     }
 }
 int topsort()
 {
     int tot2;
     int i,j,v,temp;
     int k,flag;
     queue<int>q;
     int now;

     tot2=flag=temp=0;
     for(i=0;i<n;i++)
     {
         if(father[i]==i)
         {
             tot2++;
             if(!indegree[i])    {temp++;q.push(i);}
             if(temp>1)   flag=2;
         }
     }

     k=0;
     while(!q.empty())
     {
         now=q.front();
         q.pop();
         k++;
         indegree[now]--;
         temp=0;
         for(j=head[now];j!=-1;j=eage[j].next)
         {
             v=eage[j].to;
             indegree[v]--;
             if(!indegree[v])    {temp++;q.push(v);}
         }
         if(temp>1)   flag=2;
     }
     if(k<tot2)   flag=1;
     return flag;
 }
 int main()
 {
     while(scanf("%d%d",&n,&m)!=-1)
     {
         ans=0;
         get_map();
         if(!ans)        ans=topsort();
         if(!ans)        printf("OK\n");
         else if(ans==1) printf("CONFLICT\n");
         else            printf("UNCERTAIN\n");
     }
     return 0;
 }