Poj 1094 Sorting It All Out

Sorting It All Out

Time Limit: 1000MS		Memory Limit: 10000K
Total Submissions: 30086		Accepted: 10400

Description

An ascending sorted sequence of distinct values is one in which some form of a less-than operator is used to order the elements from smallest to largest. For example, the sorted sequence A, B, C, D implies that A < B, B < C and C < D. in this problem, we will give you a set of relations of the form A < B and ask you to determine whether a sorted order has been specified or not.

Input

Input consists of multiple problem instances. Each instance starts with a line containing two positive integers n and m. the first value indicated the number of objects to sort, where 2 <= n <= 26. The objects to be sorted will be the first n characters of the uppercase alphabet. The second value m indicates the number of relations of the form A < B which will be given in this problem instance. Next will be m lines, each containing one such relation consisting of three characters: an uppercase letter, the character "<" and a second uppercase letter. No letter will be outside the range of the first n letters of the alphabet. Values of n = m = 0 indicate end of input.

Output

For each problem instance, output consists of one line. This line should be one of the following three: 

Sorted sequence determined after xxx relations: yyy...y. 
Sorted sequence cannot be determined. 
Inconsistency found after xxx relations. 

where xxx is the number of relations processed at the time either a sorted sequence is determined or an inconsistency is found, whichever comes first, and yyy...y is the sorted, ascending sequence. 

Sample Input

4 6
A<B
A<C
B<C
C<D
B<D
A<B
3 2A<BB<A26 1A<Z
10 40
C<I
E<G
A<J
F<B
D<E
F<D
C<B
E<H
G<I
D<B
C<H
A<B
J<I
D<G
A<E
C<G
E<B
H<G
C<A
F<J
B<G
D<J
E<J
D<H
C<F
B<J
G<J
B<H
D<A
F<I
A<H
C<E
F<H
A<G
B<I
F<A
H<J
F<G
F<E
C<J0 0

Sample Output

Sorted sequence determined after 4 relations: ABCD.
Inconsistency found after 2 relations.
Sorted sequence cannot be determined.
Sorted sequence determined after 29 relations: CFDAEBHGJI.




 这两天心思有点乱，积极改善！！题目大意逗弄错了 - -。
就是判断的输入的所有行里，每次输入是否会有上边的3种情况出现。
思路是：  通过每次输入进入fi()函数里判断当前的关系中有多少入度为零。如果当前0度的数目>1则不能判断各顺序
如果度数==0，则有环出现

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
int du[400],d2[400],q[400],Map[400][400];
char s[80];
int fi(int n)
{
    int i,j,k,m,pos,flag=1;
    int c=0;
    for(i=0;i<n;i++)
    {
        d2[i]=du[i];
    }
    for(i=0;i<n;i++)
    {
        m=0;
        for(j=0;j<n;j++)
            if(d2[j]==0)
            {
                m++;
                pos=j;
            }
        if(m==0)
            return 0;
        if(m>1)
            flag=-1;
        q[c++]=pos;
        d2[pos]=-1;<span id="transmark"></span>
        for(j=0;j<n;j++)
            if(Map[pos][j])
                d2[j]--;
    }
    return flag;
}
int main()
{
    int n,m,i,j,k,bj,x,y,z;
    ios::sync_with_stdio(false);
    while(cin>>n>>m&&n&&m)
    {
        z=bj=0;
        memset(Map,0,sizeof(Map));
        memset(du,0,sizeof(du));
        for(i=1;i<=m;i++)
        {
            cin>>s;
            if(bj)
                continue;
            x=s[0]-'A';
            y=s[2]-'A';
            if(Map[x][y]==0)
            {
                Map[x][y]=1;
                du[y]++;
            }
            k=fi(n);
            if( k==1 )
            {
                printf("Sorted sequence determined after %d relations: ",i);
                for(int j=0;j<n;j++)
                    printf("%c",q[j]+'A');
                printf(".\n");
                bj=1;
            }
            else if(k==0)
            {
                printf("Inconsistency found after %d relations.\n",i);
                bj=1;
            }
        }
        if(!bj)
         printf("Sorted sequence cannot be determined.\n");
    }
    return 0;
}