Sorting It All Out

http://poj.org/problem?id=1094

  1 #include<iostream>
  2 #include<algorithm>
  3 #include<cstdio>
  4 #include<cstring>
  5 #include<vector>
  6 #include<queue>
  7 #include<cstdlib>
  8 using namespace std;
  9 const int maxn=100000+5;
 10 vector <int> g[maxn];
 11 int du[maxn],n,m,l[maxn];
 12 bool vis[1000][1000];
 13 int toposort()
 14 {
 15     memset(du,0,sizeof(du));
 16     for(int i=0; i<n; i++)
 17     {
 18         for(int j=0; j<g[i].size(); j++)
 19         {
 20             du[g[i][j]]++;
 21         }
 22     }
 23     int tot=0;
 24     bool flag=false;
 25     queue<int>q;
 26     for(int i=0; i<n; i++)
 27     {
 28         if(!du[i]) q.push(i);
 29     }
 30     while(!q.empty())
 31     {
 32         if(q.size()>1)
 33         {
 34             flag=true;
 35         }
 36         int x=q.front();
 37         q.pop();
 38         l[tot++]=x;
 39         for(int j=0; j<g[x].size(); j++)
 40         {
 41             int t=g[x][j];
 42             du[t]--;
 43             if(!du[t]) q.push(t);
 44         }
 45     }
 46     if(tot!=n) return 1;
 47     else if(flag) {
 48         return 2;
 49     }
 50     return 0;
 51 }
 52 int main()
 53 {
 54     char c1,c2;
 55     while(scanf("%d%d",&n,&m))
 56     {
 57         getchar();
 58         for(int i=0;i<maxn;i++)
 59         {
 60             g[i].clear();
 61         }
 62         bool flag1=false,flag2=false;
 63         memset(vis,0,sizeof(vis));
 64         if(n==0&&m==0) break;
 65         for(int i=1; i<=m; i++)
 66         {
 67             scanf("%c<%c",&c1,&c2);
 68             getchar();
 69             if(!flag1&&!flag2)
 70             {
 71                 if(vis[c2-'A'][c1-'A'])
 72                 {
 73                     flag1=true;
 74                     printf("Inconsistency found after %d relations.\n",i);
 75                     continue;
 76                 }
 77                 if(!vis[c1-'A'][c2-'A'])
 78                 {
 79                     g[c1-'A'].push_back(c2-'A');
 80                     vis[c1-'A'][c2-'A']=1;
 81                 }
 82                 int k=toposort();
 83                 if(k==0)
 84                 {
 85                     printf("Sorted sequence determined after %d relations: ",i);
 86                     for(int j=0; j<n; j++) printf("%c",l[j]+'A');
 87                     printf(".\n");
 88                     flag2=true;
 89                 }
 90                 else if(k==1)
 91                 {
 92                     flag1=true;
 93                     printf("Inconsistency found after %d relations.\n",i);
 94                 }
 95             }
 96         }
 97         if(!flag1&&!flag2)
 98         {
 99             printf("Sorted sequence cannot be determined.\n");
100         }
101     }
102     return 0;
103 }
View Code

 

posted @ 2013-08-20 23:15  null1019  阅读(154)  评论(0)  编辑  收藏  举报