poj1094——Sorting It All Out

拓扑排序！具体方法见：http://www.cnblogs.com/xiaosuo/archive/2010/03/26/1690302.html

#include<stdio.h> #include<string.h> struct node { int u,v; }tt[1000]; int n,m,k,dgree[27],queue[1000],rear,front; bool flag,flag1,edge[27][27],vis[27]; void NPFTP() { int i; bool equal=true; rear=0;front=0; memset(edge,true,sizeof(edge)); memset(dgree,0,sizeof(dgree)); memset(vis,true,sizeof(vis)); for(i=1;i<=k;i++){ if(edge[tt[i].u][tt[i].v]){ edge[tt[i].u][tt[i].v]=false; dgree[tt[i].v]+=1; } } for(i=1;i<=n;i++) if(dgree[i]==0){ queue[++rear]=i; vis[i]=false; } if(rear>1) equal=false; memset(edge,true,sizeof(edge)); while(rear!=front) { front++;; for(i=1;i<=k;i++){ if(tt[i].u==queue[front]&&edge[tt[i].u][tt[i].v]){ edge[tt[i].u][tt[i].v]=false; dgree[tt[i].v]--; } } for(i=1;i<=n;i++) if(dgree[i]==0&&vis[i]){ vis[i]=false; queue[++rear]=i; } if(rear-front>1) equal=false; } if(rear==n&&equal){ flag1=false;flag=false; printf("Sorted sequence determined after %d relations: ",k); for(i=1;i<=rear;i++) printf("%c",queue[i]-1+'A'); printf(".\n"); } else if(rear<n){ flag1=false;flag=false; printf("Inconsistency found after %d relations.\n",k); } } int main() { int i,j; char p[5]; while(scanf("%d%d",&n,&m)!=EOF) { flag=true;flag1=true; if(n==0&&m==0) break; for(k=1;k<=m;k++) { scanf("%s",&p); tt[k].u=p[0]-'A'+1;tt[k].v=p[2]-'A'+1; } for(k=1;k<=m;k++) { if(flag1) NPFTP(); } if(flag) printf("Sorted sequence cannot be determined.\n"); } return 0; }