POJ 1094 Topological_Sort（拓扑排序）

POJ 1094 Topological_Sort（拓扑排序）

Source Code

Problem:  1094   User: Torres 
Memory: 224K  Time: 32MS 
Language: C ++   Result: Accepted 

Source Code 
#include < iostream >
#include < algorithm >
#include < vector >

using   namespace  std;

#define  N 30

vector < vector < int >   >  G(N);
int  re[N];

int  Top_sort(vector < vector < int >   > G, int  n, int   * de)
{
    //out<<"www"<<endl;
    int i,j,k;
    memset(re,0,sizeof(re));
    int cnt=0;
    int flag1=0;
    for(i=0;i<n;i++)
    {
        int flag=0;
        for(j=0;j<n;j++)
        {
            if(de[j]==0)  
            {
                flag=1;
                for(k=j+1;!flag1&&k<n;k++)
                    if(de[k]==0)
                    {
                        flag1=1;
                        break;
                    }
                    //说明有两个可供选择的点那么就会产生不同的排列
                re[cnt++]=j;
                de[j]=-1;
                int len=G[j].size();
                for(k=0;k<len;k++)
                    if(de[G[j][k]]>0) de[G[j][k]]--;
                break;
            }
        }
        if(!flag) return 1;//矛盾
    }
    if(flag1) return -1;//不确定
    return 0;//正常
}

int  main()
{
    int n,m,i;
    char s[4];
    //freopen("in.txt","r",stdin);
    while(scanf("%d%d",&n,&m))
    {
        if(n==0&&m==0) break;
        int de[N]={0},d[N];
        int t;
        for(t=1;t<=m;t++)
        {
            scanf("%s",s);
            G[s[0]-'A'].push_back(s[2]-'A');
            de[s[2]-'A']++;
        //    for(i=0;i<n;i++)
        //        cout<<de[i]<<endl;
            memcpy(d,de,sizeof(de));
            int ans=Top_sort(G,n,d);
            if(ans==1)
            {
                printf("Inconsistency found after %d relations.\n",t);
                while(t<m) scanf("%s",s),t++;
            }
            else if(ans==0)
            {
                printf("Sorted sequence determined after %d relations: ",t);
                for(i=0;i<n;i++)
                    printf("%c",re[i]+'A');
                printf(".\n");
                while(t<m) scanf("%s",s),t++;
            }
            else if(t==m&&ans==-1)
                printf("Sorted sequence cannot be determined.\n");

        }
        for(i=0;i<n;i++)
            G[i].clear();
    }
    return 0;
}