POJ1094Sorting It All Out

Description

Input

Output

Sample Input

4 6
A<B
A<C
B<C
C<D
B<D
A<B
3 2
A<B
B<A
26 1
A<Z
0 0

Sample Output

Sorted sequence determined after 4 relations: ABCD.
Inconsistency found after 2 relations.
Sorted sequence cannot be determined.

#include <stdio.h>
#include <string>
#include <cstring>
#include <iostream>
#include <cmath>
#include <queue>
#include <stack>
#define N 1009

using namespace std;


char s[N];
int mp[27][27];
int q[N];
int deg[N];

int topo(int n)
{
    int c=0,temp[27],m,loc,flag=1;

    for(int i=1;i<=n;i++)
    temp[i]=deg[i];

    for(int i=1;i<=n;i++)
    {
        m=0;
        for(int j=1;j<=n;j++)
        if(temp[j]==0)
        {
            m++;
            loc=j;
        }

        if(m==0)
        return 0;//有环
        if(m>1)
        flag=-1;//无环

        q[c++]=loc;
        temp[loc]=-1;

        for(int j=1;j<=n;j++)
        if(mp[loc][j]==1)
        temp[j]--;

    }

   return flag;
}


int main()
{
    int n,m;
    while(~scanf("%d %d",&m,&n))
    {
        if(n==0 && m==0) break;

        memset(mp,0,sizeof mp);
        memset(deg,0,sizeof deg);

        int flag=0;

        for(int i=1;i<=n;i++)
        {
            scanf("%s",s);

            if(flag) continue;
            int a=s[0]-'A'+1;
            int b=s[2]-'A'+1;
            mp[a][b]=1;
            deg[b]++;

            int ans=topo(m);

            if(ans==0)
            {
                cout<<"Inconsistency found after "<<i<<" relations."<<endl;
                flag=1;
            }

            if(ans==1)
            {
                cout<<"Sorted sequence determined after "<<i<<" relations: ";

                for(int j=0;j<m;j++)
                printf("%c",q[j]-1+'A');
                cout<<".\n";
                flag=1;

            }
        }

        if(flag==0)
        cout<<"Sorted sequence cannot be determined."<<endl;

    }
    return 0;
}

POJ1094Sorting It All Out

原文：http://blog.csdn.net/wust_zjx/article/details/45585669